checkstyle fix

Change-Id: I5912abd81b95b2422bfb75454b0fa1b7a9d63f5a
diff --git a/providers/openflow/flow/src/main/java/org/onlab/onos/provider/of/flow/impl/OpenFlowRuleProvider.java b/providers/openflow/flow/src/main/java/org/onlab/onos/provider/of/flow/impl/OpenFlowRuleProvider.java
index f52255a..94d1282 100644
--- a/providers/openflow/flow/src/main/java/org/onlab/onos/provider/of/flow/impl/OpenFlowRuleProvider.java
+++ b/providers/openflow/flow/src/main/java/org/onlab/onos/provider/of/flow/impl/OpenFlowRuleProvider.java
@@ -62,7 +62,6 @@
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
-import java.util.concurrent.CancellationException;
 import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.ExecutionException;