Add ability to dynamically generate gateway external address

Currently reclass classify command fails to generate gateway
external ip dynamically, because it's hardcoded in reclass,
this patch fixes this.

Change-Id: I0f8424cf4546cd0d3d4371f09640db311af9c2bb
diff --git a/classes/cluster/virtual-mcp-pike-ovs/openstack/init.yml b/classes/cluster/virtual-mcp-pike-ovs/openstack/init.yml
index 487dd65..b813a5d 100644
--- a/classes/cluster/virtual-mcp-pike-ovs/openstack/init.yml
+++ b/classes/cluster/virtual-mcp-pike-ovs/openstack/init.yml
@@ -22,6 +22,7 @@
     openstack_message_queue_node03_address: ${_param:openstack_control_node03_address}
     openstack_gateway_address: 172.16.10.110
     openstack_gateway_node01_address: ${_param:openstack_gateway_address}
+    openstack_gateway_node01_external_address: 10.16.0.110
     openstack_dns_node01_address: 172.16.10.111
     openstack_dns_node02_address: 172.16.10.112
     openstack_share_node01_address: 172.16.10.130