Verify the response attributes of 'aggregate-add-remove-host' API

This patch verifies the response attributes of 'aggregate-add-remove-host'.
The response attributes of v2 and v3 are the same:
{
    "aggregate": {
        "availability_zone": "nova",
        "created_at": "2012-12-04T12:04:24.399784",
        "deleted": false,
        "deleted_at": null,
        "hosts": [],
        "id": 1,
        "metadata": {
            "availability_zone": "nova"
        },
        "name": "name",
        "updated_at": null
    }
}
The status_code is different:
v2 -> 200, v3 -> 202

Partially implements blueprint nova-api-attribute-test

Change-Id: I6f6bdc458f15f8af812fee6926e5133df09f9fa1
Merge "Verify the response attributes of 'aggregate-add-remove-host' API"