Improve Executors related logging behavior

- Specify Logger for the Executor
- Use Executor#execute instead of ExecutorService#submit for
  fire and forget type of usage.
   Note: submit() will swallow thrown Exception

Change-Id: I507b841dc3feedf4ad20a746c304518d68fb846a
diff --git a/core/store/dist/src/main/java/org/onosproject/store/flow/impl/NewDistributedFlowRuleStore.java b/core/store/dist/src/main/java/org/onosproject/store/flow/impl/NewDistributedFlowRuleStore.java
index a2b9995..7b94670 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/flow/impl/NewDistributedFlowRuleStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/flow/impl/NewDistributedFlowRuleStore.java
@@ -305,7 +305,7 @@
             msgHandlerPoolSize = newPoolSize;
             ExecutorService oldMsgHandler = messageHandlingExecutor;
             messageHandlingExecutor = Executors.newFixedThreadPool(
-                    msgHandlerPoolSize, groupedThreads("onos/store/flow", "message-handlers"));
+                    msgHandlerPoolSize, groupedThreads("onos/store/flow", "message-handlers", log));
 
             // replace previously registered handlers.
             registerMessageHandlers(messageHandlingExecutor);