Add tunnel_bridge configuration for openvswitch agent

Change-Id: I0235aa05cf86b3ed9d9620dda3f16b69ced077e3
diff --git a/lib/neutron_plugins/ovs_base b/lib/neutron_plugins/ovs_base
old mode 100644
new mode 100755
index 4e750f0..ad09a73
--- a/lib/neutron_plugins/ovs_base
+++ b/lib/neutron_plugins/ovs_base
@@ -9,6 +9,7 @@
 
 OVS_BRIDGE=${OVS_BRIDGE:-br-int}
 OVS_DATAPATH_TYPE=${OVS_DATAPATH_TYPE:-""}
+OVS_TUNNEL_BRIDGE=${OVS_TUNNEL_BRIDGE:-br-tun}
 
 function is_neutron_ovs_base_plugin {
     # Yes, we use OVS.