Verify Image attributes through Nova V2 GET API

This patch adds the JSON Schema for response of Nova V2 GET Image API
and validate the response with added JSON Schema to block the backward
incompatibility change in the future.

The response body of V2 GET Image API is below:

{
    "image": {
        "id": "70a599e0-31e7-49b7-b260-868f441e862b",
        "status": "ACTIVE",
        "updated": "2011-01-01T01:02:03Z",
        "links": [
            {
                "href": "http://openstack.example.com/v2/openstack/
                        images/70a599e0-31e7-49b7-b260-868f441e862b",
                "rel": "self"
            },
            {
                "href": "http://openstack.example.com/openstack/
                        images/70a599e0-31e7-49b7-b260-868f441e862b",
                "rel": "bookmark"
            },
            {
                "href": "http://glance.openstack.example.com/openstack/
                        images/70a599e0-31e7-49b7-b260-868f441e862b",
                "rel": "alternate",
                "type": "application/vnd.openstack.image"
            }
        ],
        "name": "fakeimage7",
        "created": "2011-01-01T01:02:03Z",
        "OS-EXT-IMG-SIZE:size": 25165824,
        "minDisk": 0,
        "minRam": 0,
        "progress": 100,
        "metadata": {
            "architecture": "x86_64",
            "auto_disk_config": "True",
            "kernel_id": "nokernel",
            "ramdisk_id": "nokernel"
        },
        "server": {
            "id": "65802d04-c684-4900-b645-a6a15f78add4",
            "links": [
                {
                    "href": "http://10.21.43.120:8774/v2/
                            f0468e49de7b4f74b6359a6dd3a72481/servers/
                            65802d04-c684-4900-b645-a6a15f78add4",
                    "rel": "self"
                }
            ]
        }
    }
}

Partially implements blueprint nova-api-attribute-test

Change-Id: I3f09f5857ad35bc9f703a0482c761ae2ec2418f1
Merge "Verify Image attributes through Nova V2 GET API"