Moving all existing volume v2 service clients to
v3 dir. These service clients will be available as
v3 service clients.
For backward compatibility, keeping all service
clients importable from volume.v2 dir with deprecation
warning.
This patch is starting patch to make volume service clients
cleanup for v3 API testing as default.
Change-Id: I5888740f94d9f1ef8ce3fac78e4ce76ae650a6fd