[ONOS-4280] Allow to add a subnet to external network after the external network is used in routers

Change-Id: Idc41e64c21b9b36422bba67b48027c8a7f337a70
diff --git a/apps/openstacknetworking/openstackrouting/src/main/java/org/onosproject/openstacknetworking/routing/OpenstackRoutingManager.java b/apps/openstacknetworking/openstackrouting/src/main/java/org/onosproject/openstacknetworking/routing/OpenstackRoutingManager.java
index edc340b..b653c5a 100644
--- a/apps/openstacknetworking/openstackrouting/src/main/java/org/onosproject/openstacknetworking/routing/OpenstackRoutingManager.java
+++ b/apps/openstacknetworking/openstackrouting/src/main/java/org/onosproject/openstacknetworking/routing/OpenstackRoutingManager.java
@@ -233,10 +233,7 @@
     @Override
     public void updateRouter(OpenstackRouter openstackRouter) {
         if (openstackRouter.gatewayExternalInfo().externalFixedIps().size() > 0) {
-            Ip4Address externalIp = openstackRouter.gatewayExternalInfo().externalFixedIps()
-                    .values().stream().findFirst().orElse(null);
-            OpenstackRouter router = getRouterfromExternalIp(externalIp);
-            checkExternalConnection(router, getOpenstackRouterInterface(router));
+            checkExternalConnection(openstackRouter, getOpenstackRouterInterface(openstackRouter));
         } else {
             unsetExternalConnection();
         }