Add uptimes to device and cluster REST APIs

Change-Id: I0ccdf4e33135be4bcfd1674a76ff4b39e992268b
diff --git a/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/VirtualNetworkDeviceManager.java b/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/VirtualNetworkDeviceManager.java
index 3f808b4..601a05d 100644
--- a/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/VirtualNetworkDeviceManager.java
+++ b/incubator/net/src/main/java/org/onosproject/incubator/net/virtual/impl/VirtualNetworkDeviceManager.java
@@ -182,6 +182,12 @@
         return null;
     }
 
+    @Override
+    public long getLastUpdatedInstant(DeviceId deviceId) {
+        // TODO not supported at this time
+        return 0;
+    }
+
     /**
      * Translates VirtualNetworkEvent to DeviceEvent.
      */