Fix: do not add Stateful SNAT downstream rule in stateless case

Change-Id: I0fe8e75179baa291d864b1f1b0a64b92e6235389
diff --git a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingSnatHandler.java b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingSnatHandler.java
index 8efabcd..c7c0ef3 100644
--- a/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingSnatHandler.java
+++ b/apps/openstacknetworking/app/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackRoutingSnatHandler.java
@@ -865,6 +865,10 @@
 
     private void setStatefulDownstreamRules(Router osRouter, boolean install) {
 
+        if (!getStatefulSnatFlag()) {
+            return;
+        }
+
         IpAddress natAddress = getExternalIp(osRouter, osNetworkAdminService);
         if (natAddress == null) {
             return;