Setting up backend images for VCP VM's

This patchset is required by: #/c/25365/

Change-Id: I2aa73d3f16b10d2d7597a89f46fdeed6bf268661
diff --git a/salt/control/placement/ovs/compact.yml b/salt/control/placement/ovs/compact.yml
index 3102b3e..de0569c 100644
--- a/salt/control/placement/ovs/compact.yml
+++ b/salt/control/placement/ovs/compact.yml
@@ -6,6 +6,8 @@
     openstack_gateway_node01_hostname: gtw01
     openstack_gateway_node02_hostname: gtw02
     openstack_gateway_node03_hostname: gtw03
+    salt_control_xenial_image_backend: /var/lib/libvirt/images/backends/xenial.qcow2
+    openstack_gateway_backend_image: ${_param:salt_control_xenial_image_backend}
   salt:
     control:
       cluster:
@@ -14,15 +16,18 @@
             gtw01:
               name: ${_param:openstack_gateway_node01_hostname}
               image: ${_param:salt_control_xenial_image}
+              backend: ${_param:openstack_gateway_backend_image}
               provider: ${_param:infra_kvm_node01_hostname}.${_param:cluster_domain}
               size: openstack.gateway
             gtw02:
               name: ${_param:openstack_gateway_node02_hostname}
               image: ${_param:salt_control_xenial_image}
+              backend: ${_param:openstack_gateway_backend_image}
               provider: ${_param:infra_kvm_node02_hostname}.${_param:cluster_domain}
               size: openstack.gateway
             gtw03:
               name: ${_param:openstack_gateway_node03_hostname}
               image: ${_param:salt_control_xenial_image}
+              backend: ${_param:openstack_gateway_backend_image}
               provider: ${_param:infra_kvm_node03_hostname}.${_param:cluster_domain}
-              size: openstack.gateway
\ No newline at end of file
+              size: openstack.gateway