Task health checking by app version.

- HC manager now tracks checks by appId + version
- Added TaskTracker.getVersion
- Call healthCheckManager.addAllFor from
  DeploymentActor during start and restart to
  avoid a race between health check reconciliation
  and the initial task health update from the
  executor health check system
- Added missing health check reconciliation calls
- Fixes #688
- Fixes #697

### Here is an app running with command health checks:

```
connor@iota:marathon (697-health-checks-by-app-version) $ http mesos.vm:8080/v2/apps?embed=apps.tasks
HTTP/1.1 200 OK
Content-Type: application/json
Server: Jetty(8.y.z-SNAPSHOT)
Transfer-Encoding: chunked

{
    "apps": [
        {
            "args": null, 
            "backoffFactor": 1.15, 
            "backoffSeconds": 1, 
            "cmd": "python3 -m http.server 8080", 
            "constraints": [], 
            "container": {
                "docker": {
                    "image": "python:3", 
                    "network": "BRIDGE", 
                    "portMappings": [
                        {
                            "containerPort": 8080, 
                            "hostPort": 0, 
                            "protocol": "tcp", 
                            "servicePort": 9000
                        }, 
                        {
                            "containerPort": 161, 
                            "hostPort": 0, 
                            "protocol": "udp", 
                            "servicePort": 10000
                        }
                    ]
                }, 
                "type": "DOCKER", 
                "volumes": []
            }, 
            "cpus": 0.25, 
            "dependencies": [], 
            "deployments": [], 
            "disk": 0.0, 
            "env": {}, 
            "executor": "", 
            "healthChecks": [
                {
                    "command": {
                        "value": "curl -f -X GET http://$HOST:$PORT"
                    }, 
                    "gracePeriodSeconds": 5, 
                    "intervalSeconds": 20, 
                    "maxConsecutiveFailures": 3, 
                    "path": "/", 
                    "portIndex": 0, 
                    "protocol": "COMMAND", 
                    "timeoutSeconds": 20
                }
            ], 
            "id": "/bridged-webapp", 
            "instances": 2, 
            "mem": 64.0, 
            "ports": [
                9000, 
                10000
            ], 
            "requirePorts": false, 
            "storeUrls": [], 
            "tasks": [
                {
                    "appId": "/bridged-webapp", 
                    "healthCheckResults": [
                        {
                            "alive": true, 
                            "consecutiveFailures": 0, 
                            "firstSuccess": "2014-10-29T22:34:16.686Z", 
                            "lastFailure": null, 
                            "lastSuccess": "2014-10-29T22:34:16.686Z", 
                            "taskId": "bridged-webapp.b5da4126-5fbb-11e4-ad9b-6e94cab8a4fe"
                        }
                    ], 
                    "host": "10.141.141.10", 
                    "id": "bridged-webapp.b5da4126-5fbb-11e4-ad9b-6e94cab8a4fe", 
                    "ports": [
                        31002, 
                        31003
                    ], 
                    "stagedAt": "2014-10-29T22:34:14.248Z", 
                    "startedAt": "2014-10-29T22:34:31.572Z", 
                    "version": "2014-10-29T22:29:38.355Z"
                }, 
                {
                    "appId": "/bridged-webapp", 
                    "healthCheckResults": [
                        {
                            "alive": true, 
                            "consecutiveFailures": 0, 
                            "firstSuccess": "2014-10-29T22:34:22.728Z", 
                            "lastFailure": null, 
                            "lastSuccess": "2014-10-29T22:34:22.728Z", 
                            "taskId": "bridged-webapp.b83d8588-5fbb-11e4-ad9b-6e94cab8a4fe"
                        }
                    ], 
                    "host": "10.141.141.10", 
                    "id": "bridged-webapp.b83d8588-5fbb-11e4-ad9b-6e94cab8a4fe", 
                    "ports": [
                        31004, 
                        31005
                    ], 
                    "stagedAt": "2014-10-29T22:34:18.255Z", 
                    "startedAt": "2014-10-29T22:34:31.579Z", 
                    "version": "2014-10-29T22:29:38.355Z"
                }
            ], 
            "tasksRunning": 2, 
            "tasksStaged": 0, 
            "upgradeStrategy": {
                "minimumHealthCapacity": 1.0
            }, 
            "uris": [], 
            "user": null, 
            "version": "2014-10-29T22:29:38.355Z"
        }
    ]
}
```

### Swapping the command health check for an HTTP health check:

```
connor@iota:marathon (697-health-checks-by-app-version) $ http put mesos.vm:8080/v2/apps/bridged-webapp < examples/bridge-http.json
HTTP/1.1 200 OK
Content-Type: application/json
Server: Jetty(8.y.z-SNAPSHOT)
Transfer-Encoding: chunked

{
    "deploymentId": "cb8cfa2d-93e6-4108-83e6-458bd1dc7581", 
    "version": "2014-10-29T22:35:14.032Z"
}
```

```
connor@iota:marathon (697-health-checks-by-app-version) $ http mesos.vm:8080/v2/apps?embed=apps.tasks
HTTP/1.1 200 OK
Content-Type: application/json
Server: Jetty(8.y.z-SNAPSHOT)
Transfer-Encoding: chunked

{
    "apps": [
        {
            "args": null, 
            "backoffFactor": 1.15, 
            "backoffSeconds": 1, 
            "cmd": "python3 -m http.server 8080", 
            "constraints": [], 
            "container": {
                "docker": {
                    "image": "python:3", 
                    "network": "BRIDGE", 
                    "portMappings": [
                        {
                            "containerPort": 8080, 
                            "hostPort": 0, 
                            "protocol": "tcp", 
                            "servicePort": 9000
                        }, 
                        {
                            "containerPort": 161, 
                            "hostPort": 0, 
                            "protocol": "udp", 
                            "servicePort": 10000
                        }
                    ]
                }, 
                "type": "DOCKER", 
                "volumes": []
            }, 
            "cpus": 0.25, 
            "dependencies": [], 
            "deployments": [], 
            "disk": 0.0, 
            "env": {}, 
            "executor": "", 
            "healthChecks": [
                {
                    "command": null, 
                    "gracePeriodSeconds": 5, 
                    "intervalSeconds": 20, 
                    "maxConsecutiveFailures": 3, 
                    "path": "/", 
                    "portIndex": 0, 
                    "protocol": "HTTP", 
                    "timeoutSeconds": 20
                }
            ], 
            "id": "/bridged-webapp", 
            "instances": 2, 
            "mem": 64.0, 
            "ports": [
                9000, 
                10000
            ], 
            "requirePorts": false, 
            "storeUrls": [], 
            "tasks": [
                {
                    "appId": "/bridged-webapp", 
                    "healthCheckResults": [
                        {
                            "alive": true, 
                            "consecutiveFailures": 0, 
                            "firstSuccess": "2014-10-29T22:35:34.102Z", 
                            "lastFailure": null, 
                            "lastSuccess": "2014-10-29T22:35:54.123Z", 
                            "taskId": "bridged-webapp.dad89f41-5fbb-11e4-ad9b-6e94cab8a4fe"
                        }
                    ], 
                    "host": "10.141.141.10", 
                    "id": "bridged-webapp.dad89f41-5fbb-11e4-ad9b-6e94cab8a4fe", 
                    "ports": [
                        31006, 
                        31007
                    ], 
                    "stagedAt": "2014-10-29T22:35:16.313Z", 
                    "startedAt": "2014-10-29T22:36:01.568Z", 
                    "version": "2014-10-29T22:35:14.032Z"
                }, 
                {
                    "appId": "/bridged-webapp", 
                    "healthCheckResults": [
                        {
                            "alive": true, 
                            "consecutiveFailures": 0, 
                            "firstSuccess": "2014-10-29T22:35:54.125Z", 
                            "lastFailure": null, 
                            "lastSuccess": "2014-10-29T22:35:54.125Z", 
                            "taskId": "bridged-webapp.e62e62d5-5fbb-11e4-ad9b-6e94cab8a4fe"
                        }
                    ], 
                    "host": "10.141.141.10", 
                    "id": "bridged-webapp.e62e62d5-5fbb-11e4-ad9b-6e94cab8a4fe", 
                    "ports": [
                        31008, 
                        31009
                    ], 
                    "stagedAt": "2014-10-29T22:35:35.330Z", 
                    "startedAt": "2014-10-29T22:36:01.576Z", 
                    "version": "2014-10-29T22:35:14.032Z"
                }
            ], 
            "tasksRunning": 2, 
            "tasksStaged": 0, 
            "upgradeStrategy": {
                "minimumHealthCapacity": 1.0
            }, 
            "uris": [], 
            "user": null, 
            "version": "2014-10-29T22:35:14.032Z"
        }
    ]
}
```

### Swapping the HTTP health check back to a command health check:

```
connor@iota:marathon (697-health-checks-by-app-version) $ http put mesos.vm:8080/v2/apps/bridged-webapp < examples/bridge-command.json
HTTP/1.1 200 OK
Content-Type: application/json
Server: Jetty(8.y.z-SNAPSHOT)
Transfer-Encoding: chunked

{
    "deploymentId": "9fbb78ca-bf9a-4669-8703-8e8ede78e057", 
    "version": "2014-10-29T22:36:28.015Z"
}
```

```
connor@iota:marathon (697-health-checks-by-app-version) $ http mesos.vm:8080/v2/apps?embed=apps.tasks
HTTP/1.1 200 OK
Content-Type: application/json
Server: Jetty(8.y.z-SNAPSHOT)
Transfer-Encoding: chunked

{
    "apps": [
        {
            "args": null, 
            "backoffFactor": 1.15, 
            "backoffSeconds": 1, 
            "cmd": "python3 -m http.server 8080", 
            "constraints": [], 
            "container": {
                "docker": {
                    "image": "python:3", 
                    "network": "BRIDGE", 
                    "portMappings": [
                        {
                            "containerPort": 8080, 
                            "hostPort": 0, 
                            "protocol": "tcp", 
                            "servicePort": 9000
                        }, 
                        {
                            "containerPort": 161, 
                            "hostPort": 0, 
                            "protocol": "udp", 
                            "servicePort": 10000
                        }
                    ]
                }, 
                "type": "DOCKER", 
                "volumes": []
            }, 
            "cpus": 0.25, 
            "dependencies": [], 
            "deployments": [], 
            "disk": 0.0, 
            "env": {}, 
            "executor": "", 
            "healthChecks": [
                {
                    "command": {
                        "value": "curl -f -X GET http://$HOST:$PORT"
                    }, 
                    "gracePeriodSeconds": 5, 
                    "intervalSeconds": 20, 
                    "maxConsecutiveFailures": 3, 
                    "path": "/", 
                    "portIndex": 0, 
                    "protocol": "COMMAND", 
                    "timeoutSeconds": 20
                }
            ], 
            "id": "/bridged-webapp", 
            "instances": 2, 
            "mem": 64.0, 
            "ports": [
                9000, 
                10000
            ], 
            "requirePorts": false, 
            "storeUrls": [], 
            "tasks": [
                {
                    "appId": "/bridged-webapp", 
                    "healthCheckResults": [
                        {
                            "alive": true, 
                            "consecutiveFailures": 0, 
                            "firstSuccess": "2014-10-29T22:36:33.121Z", 
                            "lastFailure": null, 
                            "lastSuccess": "2014-10-29T22:36:33.121Z", 
                            "taskId": "bridged-webapp.07000729-5fbc-11e4-ad9b-6e94cab8a4fe"
                        }
                    ], 
                    "host": "10.141.141.10", 
                    "id": "bridged-webapp.07000729-5fbc-11e4-ad9b-6e94cab8a4fe", 
                    "ports": [
                        31010, 
                        31011
                    ], 
                    "stagedAt": "2014-10-29T22:36:30.391Z", 
                    "startedAt": "2014-10-29T22:37:01.534Z", 
                    "version": "2014-10-29T22:36:28.015Z"
                }, 
                {
                    "appId": "/bridged-webapp", 
                    "healthCheckResults": [
                        {
                            "alive": true, 
                            "consecutiveFailures": 0, 
                            "firstSuccess": "2014-10-29T22:36:49.214Z", 
                            "lastFailure": null, 
                            "lastSuccess": "2014-10-29T22:36:49.214Z", 
                            "taskId": "bridged-webapp.108c2e4f-5fbc-11e4-ad9b-6e94cab8a4fe"
                        }
                    ], 
                    "host": "10.141.141.10", 
                    "id": "bridged-webapp.108c2e4f-5fbc-11e4-ad9b-6e94cab8a4fe", 
                    "ports": [
                        31002, 
                        31003
                    ], 
                    "stagedAt": "2014-10-29T22:36:46.408Z", 
                    "startedAt": "2014-10-29T22:37:01.540Z", 
                    "version": "2014-10-29T22:36:28.015Z"
                }
            ], 
            "tasksRunning": 2, 
            "tasksStaged": 0, 
            "upgradeStrategy": {
                "minimumHealthCapacity": 1.0
            }, 
            "uris": [], 
            "user": null, 
            "version": "2014-10-29T22:36:28.015Z"
        }
    ]
}
```

### Adding the HTTP health check:

```
connor@iota:marathon (697-health-checks-by-app-version) $ http put mesos.vm:8080/v2/apps/bridged-webapp < examples/bridge.json
HTTP/1.1 200 OK
Content-Type: application/json
Server: Jetty(8.y.z-SNAPSHOT)
Transfer-Encoding: chunked

{
    "deploymentId": "c170724e-a8db-4883-8275-dc05faec6cc7", 
    "version": "2014-10-29T22:42:37.485Z"
}
```

```
connor@iota:marathon (697-health-checks-by-app-version) $ http mesos.vm:8080/v2/apps?embed=apps.tasks
HTTP/1.1 200 OK
Content-Type: application/json
Server: Jetty(8.y.z-SNAPSHOT)
Transfer-Encoding: chunked

{
    "apps": [
        {
            "args": null, 
            "backoffFactor": 1.15, 
            "backoffSeconds": 1, 
            "cmd": "python3 -m http.server 8080", 
            "constraints": [], 
            "container": {
                "docker": {
                    "image": "python:3", 
                    "network": "BRIDGE", 
                    "portMappings": [
                        {
                            "containerPort": 8080, 
                            "hostPort": 0, 
                            "protocol": "tcp", 
                            "servicePort": 9000
                        }, 
                        {
                            "containerPort": 161, 
                            "hostPort": 0, 
                            "protocol": "udp", 
                            "servicePort": 10000
                        }
                    ]
                }, 
                "type": "DOCKER", 
                "volumes": []
            }, 
            "cpus": 0.25, 
            "dependencies": [], 
            "deployments": [], 
            "disk": 0.0, 
            "env": {}, 
            "executor": "", 
            "healthChecks": [
                {
                    "command": null, 
                    "gracePeriodSeconds": 5, 
                    "intervalSeconds": 20, 
                    "maxConsecutiveFailures": 3, 
                    "path": "/", 
                    "portIndex": 0, 
                    "protocol": "HTTP", 
                    "timeoutSeconds": 20
                }, 
                {
                    "command": {
                        "value": "curl -f -X GET http://$HOST:$PORT"
                    }, 
                    "gracePeriodSeconds": 5, 
                    "intervalSeconds": 20, 
                    "maxConsecutiveFailures": 3, 
                    "path": "/", 
                    "portIndex": 0, 
                    "protocol": "COMMAND", 
                    "timeoutSeconds": 20
                }
            ], 
            "id": "/bridged-webapp", 
            "instances": 2, 
            "mem": 64.0, 
            "ports": [
                9000, 
                10000
            ], 
            "requirePorts": false, 
            "storeUrls": [], 
            "tasks": [
                {
                    "appId": "/bridged-webapp", 
                    "healthCheckResults": [
                        {
                            "alive": true, 
                            "consecutiveFailures": 0, 
                            "firstSuccess": "2014-10-29T22:42:57.587Z", 
                            "lastFailure": null, 
                            "lastSuccess": "2014-10-29T22:43:37.608Z", 
                            "taskId": "bridged-webapp.e6256cc3-5fbc-11e4-ad9b-6e94cab8a4fe"
                        }, 
                        {
                            "alive": true, 
                            "consecutiveFailures": 0, 
                            "firstSuccess": "2014-10-29T22:42:47.031Z", 
                            "lastFailure": null, 
                            "lastSuccess": "2014-10-29T22:42:47.031Z", 
                            "taskId": "bridged-webapp.e6256cc3-5fbc-11e4-ad9b-6e94cab8a4fe"
                        }
                    ], 
                    "host": "10.141.141.10", 
                    "id": "bridged-webapp.e6256cc3-5fbc-11e4-ad9b-6e94cab8a4fe", 
                    "ports": [
                        31000, 
                        31001
                    ], 
                    "stagedAt": "2014-10-29T22:42:44.768Z", 
                    "startedAt": "2014-10-29T22:43:31.519Z", 
                    "version": "2014-10-29T22:42:37.485Z"
                }, 
                {
                    "appId": "/bridged-webapp", 
                    "healthCheckResults": [
                        {
                            "alive": true, 
                            "consecutiveFailures": 0, 
                            "firstSuccess": "2014-10-29T22:42:57.585Z", 
                            "lastFailure": null, 
                            "lastSuccess": "2014-10-29T22:43:37.614Z", 
                            "taskId": "bridged-webapp.e290d451-5fbc-11e4-ad9b-6e94cab8a4fe"
                        }, 
                        {
                            "alive": true, 
                            "consecutiveFailures": 0, 
                            "firstSuccess": "2014-10-29T22:42:40.988Z", 
                            "lastFailure": null, 
                            "lastSuccess": "2014-10-29T22:42:40.988Z", 
                            "taskId": "bridged-webapp.e290d451-5fbc-11e4-ad9b-6e94cab8a4fe"
                        }
                    ], 
                    "host": "10.141.141.10", 
                    "id": "bridged-webapp.e290d451-5fbc-11e4-ad9b-6e94cab8a4fe", 
                    "ports": [
                        31004, 
                        31005
                    ], 
                    "stagedAt": "2014-10-29T22:42:38.761Z", 
                    "startedAt": "2014-10-29T22:43:31.527Z", 
                    "version": "2014-10-29T22:42:37.485Z"
                }
            ], 
            "tasksRunning": 2, 
            "tasksStaged": 0, 
            "upgradeStrategy": {
                "minimumHealthCapacity": 1.0
            }, 
            "uris": [], 
            "user": null, 
            "version": "2014-10-29T22:42:37.485Z"
        }
    ]
}
```
This class is not threadsafe. Are we sure this is only used by one thread?