Simplify statement by using a method in standard library

Change-Id: I1c04b42017e26c864c9e147e2731a814315ca5e2
diff --git a/core/net/src/test/java/org/onosproject/net/intent/impl/MockFlowRuleService.java b/core/net/src/test/java/org/onosproject/net/intent/impl/MockFlowRuleService.java
index 8bd29bf..f23a049 100644
--- a/core/net/src/test/java/org/onosproject/net/intent/impl/MockFlowRuleService.java
+++ b/core/net/src/test/java/org/onosproject/net/intent/impl/MockFlowRuleService.java
@@ -24,13 +24,11 @@
 import org.onosproject.net.flow.FlowRuleOperations;
 import org.onosproject.net.flow.FlowRuleServiceAdapter;
 
+import java.util.Collections;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.stream.Collectors;
 
-import static org.onosproject.net.flow.FlowRuleOperation.Type.REMOVE;
-
-
 public class MockFlowRuleService extends FlowRuleServiceAdapter {
 
     final Set<FlowRule> flows = Sets.newHashSet();
@@ -87,9 +85,7 @@
 
     @Override
     public void applyFlowRules(FlowRule... flowRules) {
-        for (FlowRule flow : flowRules) {
-            flows.add(flow);
-        }
+        Collections.addAll(flows, flowRules);
     }
 
     @Override