Improves host programming introducing a pool of worker threads

Change-Id: I979693aa220e2666c13c4015435c66173624ea64
diff --git a/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java b/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
index 6cc0e74..4c66dd0 100644
--- a/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
+++ b/app/src/main/java/org/onosproject/segmentrouting/SegmentRoutingManager.java
@@ -642,6 +642,7 @@
         policyStore.destroy();
 
         mcastHandler.terminate();
+        hostHandler.terminate();
         log.info("Stopped");
     }