Enable cinder v2 api tests in volume quotas

To run cinder v2 volume quotas and volume quotas negative test,
volume_quotas_v2_client is added in services side.
We are not including xml coverage for the respective test.

Partially implements: blueprint cinder-v2-api-tests

Change-Id: Icad4d24d99d3a4f7ab6008db35fab1dfd13784e9
Merge "Enable cinder v2 api tests in volume quotas"