added backup to virtual model

Change-Id: Ibbbe22b33cb52d568b1d70229ffa4791bcc15c73
diff --git a/classes/cluster/virtual-offline-pike-ovs-dpdk/openstack/control.yml b/classes/cluster/virtual-offline-pike-ovs-dpdk/openstack/control.yml
index 75a6a48..1f8adb0 100644
--- a/classes/cluster/virtual-offline-pike-ovs-dpdk/openstack/control.yml
+++ b/classes/cluster/virtual-offline-pike-ovs-dpdk/openstack/control.yml
@@ -15,6 +15,7 @@
 - system.glusterfs.client.volume.keystone
 - system.glusterfs.server.volume.glance
 - system.glusterfs.server.volume.keystone
+- system.glusterfs.server.volume.backup
 - system.glusterfs.server.cluster
 - system.glance.control.cluster
 - system.nova.control.cluster