Support cinder volume retype

Make volume_type updatable for cinder volume resource.
Notes: this feature support in volume api v2, to raise
NotSupported exception if the volume api version is v1
for volume_type updation.

Change-Id: I4b8b658a58ad0ef09763e99e9da8948cf72fed48
Closes-Bug: #1395975
Merge "Support cinder volume retype"