Refactor: remove verbose logging message at openstack networking

Change-Id: Ibe089023ff0c4df4b45476227c69ad2c80417002
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 4a8dc7c..b3c1a1f 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
@@ -828,7 +828,7 @@
 
         IpAddress natAddress = externalGatewayIpSnatEnabled(osRouter.get(), osNetworkAdminService);
         if (natAddress == null) {
-            log.warn("NAT address is not found");
+            log.debug("NAT address is not found");
             return;
         }