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/net/src/main/java/org/onosproject/net/intent/impl/IntentManager.java b/core/net/src/main/java/org/onosproject/net/intent/impl/IntentManager.java
index 61fc0df..1fc64d6 100644
--- a/core/net/src/main/java/org/onosproject/net/intent/impl/IntentManager.java
+++ b/core/net/src/main/java/org/onosproject/net/intent/impl/IntentManager.java
@@ -200,7 +200,7 @@
         if (newNumThreads != numThreads) {
             numThreads = newNumThreads;
             ExecutorService oldWorkerExecutor = workerExecutor;
-            workerExecutor = newFixedThreadPool(numThreads, groupedThreads("onos/intent", "worker-%d"));
+            workerExecutor = newFixedThreadPool(numThreads, groupedThreads("onos/intent", "worker-%d", log));
             if (oldWorkerExecutor != null) {
                 oldWorkerExecutor.shutdown();
             }