Explicitly set connection_type to libvirt

A future merge to nova (http://review.openstack.org/2918) will require this to be set

Change-Id: I92c28336a6022c325a84d6594764779d8fe5e655
diff --git a/AUTHORS b/AUTHORS
index 84a565e..34e0474 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -10,6 +10,7 @@
 Jason Cannavale <jason.cannavale@rackspace.com>
 Jay Pipes <jaypipes@gmail.com>
 Jesse Andrews <anotherjesse@gmail.com>
+Johannes Erdfelt <johannes.erdfelt@rackspace.com>
 Justin Shepherd <galstrom21@gmail.com>
 Kiall Mac Innes <kiall@managedit.ie>
 Scott Moser <smoser@ubuntu.com>
diff --git a/stack.sh b/stack.sh
index 99a0828..307be94 100755
--- a/stack.sh
+++ b/stack.sh
@@ -1228,6 +1228,7 @@
     XEN_FIREWALL_DRIVER=${XEN_FIREWALL_DRIVER:-"nova.virt.firewall.IptablesFirewallDriver"}
     add_nova_flag "--firewall_driver=$XEN_FIREWALL_DRIVER"
 else
+    add_nova_flag "--connection_type=libvirt"
     add_nova_flag "--flat_network_bridge=$FLAT_NETWORK_BRIDGE"
     if [ -n "$FLAT_INTERFACE" ]; then
         add_nova_flag "--flat_interface=$FLAT_INTERFACE"