Verify list Image attributes through Nova V2 API

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

The response body of V2 list Image API is below:

{
    "images": [
        {
            "id": "70a599e0-31e7-49b7-b260-868f441e862b",
            "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"
        }
    ]
}

Partially implements blueprint nova-api-attribute-test

Change-Id: I2afaa884e7bc5b9a8efe748f1ccfc031f301616e
Merge commit 'refs/changes/65/81565/2' of git://gold.eng.hq.xensource.com/git/github/openstack/tempest into tmpbranch