Objective tracker doesn't need to react to port events

Ported from onos-1.2 branch.

Change-Id: I73ce4d09a0d8f9ba24d335798187de83f515d5a1
(cherry picked from commit e0ec88bd)

@@ -390,19 +390,27 @@ public class ObjectiveTracker implements ObjectiveTrackerService {
         @Override
         public void event(DeviceEvent event) {
             DeviceEvent.Type type = event.type();
-            if (type == DeviceEvent.Type.PORT_ADDED ||
-                type == DeviceEvent.Type.PORT_UPDATED ||
-                type == DeviceEvent.Type.PORT_REMOVED) {
-                // skip port events for now
-                return;
-            }
+            switch (type) {
+            case DEVICE_ADDED:
+            case DEVICE_AVAILABILITY_CHANGED:
+            case DEVICE_REMOVED:
+            case DEVICE_SUSPENDED:
+            case DEVICE_UPDATED:
                 DeviceId id = event.subject().id();
                 // TODO we need to check whether AVAILABILITY_CHANGED means up or down
                 boolean available = (type == DeviceEvent.Type.DEVICE_AVAILABILITY_CHANGED ||
                         type == DeviceEvent.Type.DEVICE_ADDED ||
                         type == DeviceEvent.Type.DEVICE_UPDATED);
                 executorService.execute(new DeviceAvailabilityHandler(id, available));
-
+                break;
+            case PORT_ADDED:
+            case PORT_REMOVED:
+            case PORT_UPDATED:
+            case PORT_STATS_UPDATED:
+            default:
+                // Don't handle port events for now
+                break;
+            }
         }
     }