DistributedFlowRuleStore related fixes

- handle no master for Device case
- Changed failed item type to FlowRule

Change-Id: If6c85751759cf6ba9ab0ed0384cbe1bf08a5d572
diff --git a/core/net/src/test/java/org/onlab/onos/net/flow/impl/FlowRuleManagerTest.java b/core/net/src/test/java/org/onlab/onos/net/flow/impl/FlowRuleManagerTest.java
index 2bb0965..b986d6d 100644
--- a/core/net/src/test/java/org/onlab/onos/net/flow/impl/FlowRuleManagerTest.java
+++ b/core/net/src/test/java/org/onlab/onos/net/flow/impl/FlowRuleManagerTest.java
@@ -555,7 +555,7 @@
             @Override
             public CompletedBatchOperation get()
                     throws InterruptedException, ExecutionException {
-                return new CompletedBatchOperation(true, Collections.<FlowEntry>emptySet());
+                return new CompletedBatchOperation(true, Collections.<FlowRule>emptySet());
             }
 
             @Override