A recent patch [1] added support for lvm ephemeral storage for nova,
but at the cost of initializing a default lvm volume group even if it
was not required. This change ensures that init of the default volume
group is only performed when nova and/or cinder are configured to use
lvm.
1: https://review.openstack.org/#/c/132333
Change-Id: I7634ca0ed0ffe1b13464e4d66744918f85149f2e
Closes-Bug: #1414820