Enable updating the status of a volume

Expose the functionality of the 'cinder reset-state' command in the UI.
As is the case with the 'cinder reset-state' command, this change
permits an operator to select any valid status, regardless of the
current status of the volume.

Implements: blueprint cinder-reset-volume-state
Change-Id: I45180e989fb535bfd1c5bc9123bf70e4b2e24f1b
Merge "Enable updating the status of a volume"