[Gate fix] Fix volumes_client AttributeError

This commit fixes AttributeErrors related to a recent Tempest
commit Icc2e12f06c3b4899f934f000e191552f4a5cd2a9 which changed
the names of certain clients that are instantiated in
tempest.clients. This commit changes the clients that no longer
exist to the appropriately versioned client.

Change-Id: I1d70f69dd35aeae320a7db4f0fc8f1bab34b37b4
9 files changed