Enable v2 api for volume and snapshot tests

For volume action tests, name field of the volume is updated with
the cinder v2 api.
For snapshot action tests,admin_snapshots_client is moved to base class
and name field of the snapshot is updated.

Partially implements: blueprint cinder-v2-api-tests

Change-Id: Iba7fd236c752ea15b73fd308ec6e3475cf42af9c
Merge "Enable v2 api for volume and snapshot tests"