Verify update host Nova V2/V3 APIs attributes

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

The response body of update host V2 API is below:

{
    "host": "%(host_name)s",
    "maintenance_mode": "off_maintenance",
    "status": "enabled"
}

The response body of update host V3 API is below:
{
    "host": {
        "host": "%(host_name)s",
        "maintenance_mode": "off_maintenance",
        "status": "enabled"
    }
}

Partially implements blueprint nova-api-attribute-test

Change-Id: Idecedd2bbe98444b07dcf328bc73ca84e68a197a
Merge "Verify update host Nova V2/V3 APIs attributes"