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/app/GossipApplicationStore.java b/core/store/dist/src/main/java/org/onosproject/store/app/GossipApplicationStore.java
index 51f759a..36699b0 100644
--- a/core/store/dist/src/main/java/org/onosproject/store/app/GossipApplicationStore.java
+++ b/core/store/dist/src/main/java/org/onosproject/store/app/GossipApplicationStore.java
@@ -68,6 +68,7 @@
 import static com.google.common.collect.Multimaps.newSetMultimap;
 import static com.google.common.collect.Multimaps.synchronizedSetMultimap;
 import static com.google.common.io.ByteStreams.toByteArray;
+import static java.util.concurrent.Executors.newSingleThreadScheduledExecutor;
 import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import static org.onlab.util.Tools.groupedThreads;
 import static org.onlab.util.Tools.randomDelay;
@@ -138,10 +139,10 @@
                 .register(MultiValuedTimestamp.class)
                 .register(InternalState.class);
 
-        executor = Executors.newSingleThreadScheduledExecutor(groupedThreads("onos/app", "store"));
+        executor = newSingleThreadScheduledExecutor(groupedThreads("onos/app", "store", log));
 
         messageHandlingExecutor = Executors.newSingleThreadExecutor(
-                groupedThreads("onos/store/app", "message-handler"));
+                groupedThreads("onos/store/app", "message-handler", log));
 
         clusterCommunicator.<String, byte[]>addSubscriber(APP_BITS_REQUEST,
                                                           bytes -> new String(bytes, Charsets.UTF_8),