Verify "get version" API response attributes

Now most attributes of Nova v2/v3 APIs are not checked in Tempest,
and this patch adds some tests which check these attributes to block
the backward incompatibility change in the future.

This patch adds the checks of "get version" API responses.
The response body of this API is the following:

{
    "version":{
        'id': 'v3.0',
        'links': [
            {
                'href': 'http://127.0.0.1:8774/v3/'
                'rel': 'self'
            },
            {
                'href': 'http://docs.openstack.org/api/...'
                'rel': 'describedby'
                'type': 'application/pdf'
            },
            {
                'href': 'http://docs.openstack.org/api/...'
                'rel': 'describedby'
                'type': 'application/vnd.sun.wadl+xml'
            },
        ],
        'media-types': [
            {
                'base': 'application/json'
                'type': 'application/vnd.openstack.compute+...'
            },
        },
        'status': 'EXPERIMENTAL',
        'updated': '2013-07-23T11:33:21Z',
    }
}

Partially implements blueprint nova-api-attribute-test

Change-Id: Ia8e03aad49c524e5c3df110f0737eee3262b93e6
Merge "Verify "get version" API response attributes"