'groups' in cinder quota is not marked as translatable in
the default quota table. 'groups' means the number of volume generic groups
in Cinder, but 'groups' is too generic, so this commit uses 'Volume Groups'
as a lable.
Also sort quota names per back-end services (nova and cinder)
Change-Id: I2deff8fcdd832e9c2a7987ef3e54017b4aa47daf
Closes-Bug: #1710775