Init default lvm volume group only if required

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
diff --git a/lib/cinder b/lib/cinder
index 6eee880..03e2e28 100644
--- a/lib/cinder
+++ b/lib/cinder
@@ -399,6 +399,10 @@
             be_type=${be%%:*}
             be_name=${be##*:}
             if type init_cinder_backend_${be_type} >/dev/null 2>&1; then
+                # Always init the default volume group for lvm.
+                if [[ "$be_type" == "lvm" ]]; then
+                    init_default_lvm_volume_group
+                fi
                 init_cinder_backend_${be_type} ${be_name}
             fi
         done