BZ #1056055 --  [RFE] create cinder-volumes VG backed by a loopback file

https://bugzilla.redhat.com/show_bug.cgi?id=1056055

The default behavior most customers expect for small to medium installations
is to run cinder-volume on the controller node. Packstack does this but
Foreman only allows a dedicated storage backend backed by iSCSI or RHS.
This patch deploys cinder-volume on the Nova or Neutron controller node if
cinder_backend_{iscsi,gluster} are both set to false. It will detect a VG
named cinder-volumes (whether backed by an iSCSI target or loopback device)
and share it via tgtd. The user must create the VG, which is also the case
with the cinder_backend_iscsi parameter for the LVM backend storage group. In
a sense this patch replicates functionality customers expect from packstack.
I tested it against the RHEL OSP 01.31.2014-1 puddle for both iSCSI and LVM
bakced Cinder from the controller node.