Sonar fixes

Rule: Use isEmpty() to check whether the collection is empty or not.

Change-Id: Ib5ab56b2263623b297db56c5cac2c2ee80e12725
diff --git a/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/VirtualNetworkFlowRuleManager.java b/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/VirtualNetworkFlowRuleManager.java
index 31c1415..f6c6e2b 100644
--- a/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/VirtualNetworkFlowRuleManager.java
+++ b/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/VirtualNetworkFlowRuleManager.java
@@ -251,7 +251,7 @@
 
         @Override
         public synchronized void run() {
-            if (stages.size() > 0) {
+            if (!stages.isEmpty()) {
                 process(stages.remove(0));
             } else if (!hasFailed) {
                 fops.callback().onSuccess(fops);