Changing submit to execute in different providers for exception throwing

Change-Id: I2d93b365640e3be48de913e1a069d5f5a53eb303
diff --git a/providers/null/src/main/java/org/onosproject/provider/nil/TopologyMutationDriver.java b/providers/null/src/main/java/org/onosproject/provider/nil/TopologyMutationDriver.java
index 032692d..5abace6 100644
--- a/providers/null/src/main/java/org/onosproject/provider/nil/TopologyMutationDriver.java
+++ b/providers/null/src/main/java/org/onosproject/provider/nil/TopologyMutationDriver.java
@@ -70,7 +70,7 @@
     private List<LinkDescription> inactiveLinks;
 
     private final ExecutorService executor =
-            newSingleThreadScheduledExecutor(groupedThreads("onos/null", "topo-mutator"));
+            newSingleThreadScheduledExecutor(groupedThreads("onos/null", "topo-mutator", log));
 
     private Map<DeviceId, Set<Link>> savedLinks = Maps.newConcurrentMap();
 
@@ -99,7 +99,7 @@
         activeLinks = reduceLinks();
         inactiveLinks = Lists.newArrayList();
         adjustRate(mutationRate);
-        executor.submit(this);
+        executor.execute(this);
     }
 
     /**