Add precommit capability to openstack port service to resolve NPE

Change-Id: I91bdc24a3ba2b586b5503d35a8da4c6824c99765
diff --git a/apps/openstacknetworking/api/src/main/java/org/onosproject/openstacknetworking/api/OpenstackNetworkEvent.java b/apps/openstacknetworking/api/src/main/java/org/onosproject/openstacknetworking/api/OpenstackNetworkEvent.java
index 4f4892f..88b61be 100644
--- a/apps/openstacknetworking/api/src/main/java/org/onosproject/openstacknetworking/api/OpenstackNetworkEvent.java
+++ b/apps/openstacknetworking/api/src/main/java/org/onosproject/openstacknetworking/api/OpenstackNetworkEvent.java
@@ -69,11 +69,21 @@
         OPENSTACK_PORT_CREATED,
 
         /**
+         * Signifies that the OpenStack port will be updated.
+         */
+        OPENSTACK_PORT_PRE_UPDATE,
+
+        /**
          * Signifies that the OpenStack port is updated.
          */
         OPENSTACK_PORT_UPDATED,
 
         /**
+         * Signifies that the OpenStack port will be removed.
+         */
+        OPENSTACK_PORT_PRE_REMOVE,
+
+        /**
          * Signifies that the OpenStack port is removed.
          */
         OPENSTACK_PORT_REMOVED,