Verify the response attributes of 'get_aggregate'

This patch verifies the response attributes of 'get_aggregate'.
The response body of v2 and v3 API has the same format:

{
    "aggregate": {
        "availability_zone": "nova",
        "created_at": "2013-08-18T12:17:56.380226",
        "deleted": false,
        "deleted_at": null,
        "hosts": [],
        "id": 1,
        "metadata": {
            "availability_zone": "nova"
        },
        "name": "name",
        "updated_at": null
    }
}

Partially implements blueprint nova-api-attribute-test

Change-Id: Ic23926ee6c4e1585a9a464df2d485f51bbf87972
3 files changed