Updated openstack/openstack
Project: openstack/cinder  4e1d168aaf186339db373683e8ecb8b3dab3b247
null
Move clear_volume method to volume.utils

clear_volume was almost the same in LVM and BlockDevice drivers.
So it has been moved to utils.

Change-Id: Iadb6b8d01cf500109bb48b0d2c817109918519e0