(#13120) Add connection_type to nova::compute::libvirt

As of essex, the option connection_type is required
for compute nodes.

This commit adds the nova configuration option to the
nova::compute::libvirt class and sets it to libvirt.

manifests/compute/libvirt.pp

@@ -5,6 +5,7 @@
   $flat_network_bridge_netmask
 ) {
   nova_config { 'libvirt_type': value => $libvirt_type }
+  nova_config { 'connection_type': value => 'libvirt' }
   nova::network::bridge { $flat_network_bridge:
     ip      => $flat_network_bridge_ip,
     netmask => $flat_network_bridge_netmask,