RESTCONF notification fixes

This submission contains the restconf portion of the changes of the follwoing
submission:

https://gerrit.onosproject.org/#/c/12310/

Change-Id: I7534c8491633f0e9a6062b337a6fd79013202940
diff --git a/protocols/restconf/client/api/src/main/java/org/onosproject/protocol/restconf/RestconfNotificationEventListener.java b/protocols/restconf/client/api/src/main/java/org/onosproject/protocol/restconf/RestconfNotificationEventListener.java
new file mode 100644
index 0000000..230724b
--- /dev/null
+++ b/protocols/restconf/client/api/src/main/java/org/onosproject/protocol/restconf/RestconfNotificationEventListener.java
@@ -0,0 +1,32 @@
+/*
+ * Copyright 2016-present Open Networking Laboratory
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.onosproject.protocol.restconf;
+
+import org.onosproject.net.DeviceId;
+
+/**
+ * Notifies providers about incoming RESTCONF notification events.
+ */
+public interface RestconfNotificationEventListener<T> {
+
+    /**
+     * Handles the notification event.
+     *
+     * @param deviceId restconf device identifier
+     * @param event    event payload
+     */
+    void handleNotificationEvent(DeviceId deviceId, T event);
+}