Add missing device service to AbstractGnmiHandlerBehaviour

Change-Id: I5702c62ef0d02d5caca35dd1de0bb5ba0e9d0344
diff --git a/drivers/gnmi/src/main/java/org/onosproject/drivers/gnmi/AbstractGnmiHandlerBehaviour.java b/drivers/gnmi/src/main/java/org/onosproject/drivers/gnmi/AbstractGnmiHandlerBehaviour.java
index fda0bb5..e6d8b16 100644
--- a/drivers/gnmi/src/main/java/org/onosproject/drivers/gnmi/AbstractGnmiHandlerBehaviour.java
+++ b/drivers/gnmi/src/main/java/org/onosproject/drivers/gnmi/AbstractGnmiHandlerBehaviour.java
@@ -54,7 +54,7 @@
 
     protected boolean setupBehaviour() {
         deviceId = handler().data().deviceId();
-
+        deviceService = handler().get(DeviceService.class);
         controller = handler().get(GnmiController.class);
         client = controller.getClient(deviceId);