Verify delete aggregate attributes of Nova APIs

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

Response status of delete aggregate V2 API is 200
Response status of delete aggregate V3 API is 204

Partially implements blueprint nova-api-attribute-test

Change-Id: I24c582d9dbfe328bf9df92cf829518bdeeb2e14e
Merge "Verify delete aggregate attributes of Nova APIs"