CORD-982 Handle PORT_REMOVED event

PORT_REMOVED is triggered instead of PORT_UPDATE when OVS port is
removed since ONOS-1.9

Change-Id: I4a15fce65653147b54f6b3eea2c7103b4275ed6b
diff --git a/src/main/java/org/opencord/cordvtn/impl/CordVtnNodeManager.java b/src/main/java/org/opencord/cordvtn/impl/CordVtnNodeManager.java
index 5180480..97f5f77 100644
--- a/src/main/java/org/opencord/cordvtn/impl/CordVtnNodeManager.java
+++ b/src/main/java/org/opencord/cordvtn/impl/CordVtnNodeManager.java
@@ -818,6 +818,14 @@
                         });
                     }
                     break;
+                case PORT_REMOVED:
+                    eventExecutor.execute(() -> {
+                        log.info("Port {} is removed from {}",
+                                event.port().annotations().value(PORT_NAME),
+                                event.subject().id());
+                        bridgeHandler.portRemoved(event.port());
+                    });
+                break;
                 case DEVICE_ADDED:
                 case DEVICE_AVAILABILITY_CHANGED:
                     if (deviceService.isAvailable(device.id())) {