Set source volume to "in use" during clone

When we are cloning a volume, we now set the source volume's status
to 'in use'. This prevents a user from deleting the source volume while the
backend copies/clones the contents to the new volume.
When the cloning is complete, we reset the status to it's original
state.

Change-Id: Ie43345aba77df4671ed2b429645cf8d1af9b975b
Merge "Set source volume to "in use" during clone"