cinder: Add encrypted volumes resources
cinder: Add encrypted volumes resources

This change adds some basic coverage for attaching and detaching an
encrypted LUKS volume during an upgrade. To keep things readable a new
_wait_for_volume_update utility function is introduced and called
throughout the cinder tests when waiting for a volume to switch state or
to become bootable.

Change-Id: I894ef91a1e38775b1b56feb84612c7661046b4ba

openstack-dev/grenade,openstack-dev/grenade