Handle volume.resize.* notifications

Cinder sends a notification at the beginning and the end
of the resize process. Those notifications are volume.resize.start
and volume.resize.end. Handle them for proper usage logging.

Fixes: bug #1220377
Change-Id: I94f0c82594f2573749d124e2cc59f7f9ff4b689d
Merge "Handle volume.resize.* notifications"