Check list servers attributes of Nova APIs

This patch adds the JSON schema for Nova V2 & V3 list servers
APIs response and validate the response with added JSON schema
to block the backward incompatibility change in the future.

Response status of list servers V2 & V3 APIs is same and given below-

{
    "servers": [
        {
            "id": "22c91117-08de-4894-9aa9-6ef382400985",
            "links": [
                {
                    "href": "http://openstack.example.com/v3/servers/
                    22c91117-08de-4894-9aa9-6ef382400985",
                    "rel": "self"
                },
                {
                    "href": "http://openstack.example.com/servers/
                    22c91117-08de-4894-9aa9-6ef382400985",
                    "rel": "bookmark"
                }
            ],
            "name": "new-server-test"
        }
    ]
}

Partially implements blueprint nova-api-attribute-test

Change-Id: I5e3854011f00b468dc63eddafd7e76a9048b1997
Merge "Check list servers attributes of Nova APIs"