Don't create cinder_volumes containers on hosts without cinder-volumes VG

[Tom Cameron]

Cinder playbooks should skip creating cinder_volumes_container-* on storage hosts that do not have a volume group present for cinder volume creation. This but impacts latest Juno but has not been tested on Kilo.

Example:

Hosts storage01 and storage02 do not have a volume group named "cinder-volumes", while host storage03 does. All three hosts have containers named cinder_volumes_container. Only the volumes container on storage03 is capable of hosting cinder volumes, so the creation of cinder_volumes_container on storage01 and storage02 should be skipped.

Upon future playbook executions, if the volume group is present then the necessary containers() should be created.

[Darren Birkett (darren-birkett)]

What if the back end isn't lvm? The lack of a cinder-volumes vg should only be a concern when the back end is lvm, so any fix would need to take this into account.