Make bamboo verbose on haproxy reload errors

On haproxy reload errors, only the exit status was printed, no "Exec cmd.." and not stdout/stderr of the command, i.e.:

```
2014/10/20 13:02:31.794232 exit status 1
2014/10/20 13:02:31.794513 HAProxy: Configuration updated
```

This patch changes the error output into:

```
2014/10/20 13:02:31.767447 Exec cmd: read PIDS < /var/run/haproxy.pid; haproxy -f /etc/haproxy/haproxy.cfg -p /var/run/haproxy.pid -sf $PIDS && while ps -p $PIDS; do sleep 0.2; done 
2014/10/20 13:02:31.794232 exit status 1
2014/10/20 13:02:31.794329 Output:
[ALERT] 292/130231 (9426) : parsing [/etc/haproxy/haproxy.cfg:38] : unknown keyword 'asdf' in 'defaults' section
[ALERT] 292/130231 (9426) : Error(s) found in configuration file : /etc/haproxy/haproxy.cfg
[ALERT] 292/130231 (9426) : Fatal errors found in configuration.

2014/10/20 13:02:31.794513 HAProxy: update failed
```

Fixes #44