Handle PORT_REMOVED event when a VM removes

Also fixed OpenStack port event log

Change-Id: I0ad4a014dcb3a1fdf7ada7eb93ec80f23f42b087
diff --git a/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingHostProvider.java b/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingHostProvider.java
index fe07b9d..8ed5785 100644
--- a/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingHostProvider.java
+++ b/apps/openstacknetworking/src/main/java/org/onosproject/openstacknetworking/impl/OpenstackSwitchingHostProvider.java
@@ -239,6 +239,13 @@
                         processPortAdded(event.port());
                     });
                     break;
+                case PORT_REMOVED:
+                    deviceEventExecutor.execute(() -> {
+                        log.debug("Instance port {} is removed from {}",
+                                event.port().annotations().value(PORT_NAME),
+                                event.subject().id());
+                        processPortRemoved(event.port());
+                    });
                 default:
                     break;
             }