Add external_svc_subnet for k8s loadbalancer type service

Add external_svc_subnet field for k8s loadbalancer type service
in kuryr-kubernetes code support external service subnet
but openshift does not support yet

Signed-off-by: jihoon.o <jihoon.o@samsung.com>

roles/kuryr/templates/configmap.yaml.j2

@@ -229,6 +229,7 @@ data:
     # TODO (apuimedo): Remove the duplicated line just after this one once the
     # RDO packaging contains the upstream patch
     worker_nodes_subnet = {{ kuryr_openstack_worker_nodes_subnet_id }}
+    external_svc_subnet = {{ kuryr_openstack_external_svc_subnet_id }}
 
     [pod_vif_nested]
     worker_nodes_subnet = {{ kuryr_openstack_worker_nodes_subnet_id }}