Change return type of groupId() in FlowRule not to misusing underlying type

Change-Id: Ide90973380f79046650bc372b9ecee00cb290f6a
diff --git a/core/net/src/main/java/org/onlab/onos/net/statistic/impl/StatisticManager.java b/core/net/src/main/java/org/onlab/onos/net/statistic/impl/StatisticManager.java
index fd4b741..f1ac9b16 100644
--- a/core/net/src/main/java/org/onlab/onos/net/statistic/impl/StatisticManager.java
+++ b/core/net/src/main/java/org/onlab/onos/net/statistic/impl/StatisticManager.java
@@ -357,7 +357,7 @@
                 }
                 // FIXME: The left hand type and right hand type don't match
                 // FlowEntry.groupId() still returns a short value, not int.
-                return flowEntry.groupId() == groupId.get().id();
+                return flowEntry.groupId().equals(groupId.get());
             }
         };
     }