Updated openstack/openstack
Project: openstack/nova  956d52f1b6b2882452009ccbb139a1b32663f02f

xenapi: move find_vbd_by_number into volume utils

Above function is only used in volumeops, so moved to volume_utils.
Also added some unit tests to cover that function.

Change-Id: I1298dd35d8a41832475c6d6bd908af8f6576be82