Cherry pick gNMI and Stratum related changes to this branch

Cherry picked commits:
20211 Update gNMI version and build script
20247 [ONOS-7829] Implement AbstractGrpcClient and AbstractGrpcClientControl
20233 [ONOS-7141][ONOS-7142] Add GnmiClient and GnmiController
20234 Refactor OpenConfig gNMI device description descovery
20260 [ONOS-7831] Implement GnmiHandshaker
20270 Add Stratum driver

Change-Id: I81ad8bce45251af5909cfcac0edbcfd11c8ebf1d
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 e6d8b16..3bfca46 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
@@ -41,9 +41,8 @@
     private static final String DEVICE_REQ_TIMEOUT = "deviceRequestTimeout";
     private static final int DEFAULT_DEVICE_REQ_TIMEOUT = 60;
 
-    public static final String GNMI_SERVER_ADDR_KEY = "gnmi_ip";
-    public static final String GNMI_SERVER_PORT_KEY = "gnmi_port";
-    private static final String GNMI_SERVICE_NAME = "gnmi";
+    private static final String GNMI_SERVER_ADDR_KEY = "gnmi_ip";
+    private static final String GNMI_SERVER_PORT_KEY = "gnmi_port";
 
     protected final Logger log = LoggerFactory.getLogger(getClass());
     protected DeviceId deviceId;
@@ -66,7 +65,7 @@
         return true;
     }
 
-    protected GnmiClient createClient() {
+    GnmiClient createClient() {
         deviceId = handler().data().deviceId();
         controller = handler().get(GnmiController.class);
 
@@ -74,7 +73,7 @@
         final String serverPortString = this.data().value(GNMI_SERVER_PORT_KEY);
 
         if (serverAddr == null || serverPortString == null) {
-            log.warn("Unable to create client for {}, missing driver data key (required is {}, {}, and {})",
+            log.warn("Unable to create client for {}, missing driver data key (required is {} and {})",
                     deviceId, GNMI_SERVER_ADDR_KEY, GNMI_SERVER_PORT_KEY);
             return null;
         }
@@ -83,11 +82,10 @@
         try {
             serverPort = Integer.parseUnsignedInt(serverPortString);
         } catch (NumberFormatException e) {
-            log.error("{} is not a valid gNMI port number", serverPortString);
+            log.error("{} is not a valid port number", serverPortString);
             return null;
         }
-        GnmiClientKey clientKey =
-                new GnmiClientKey(GNMI_SERVICE_NAME, deviceId, serverAddr, serverPort);
+        GnmiClientKey clientKey = new GnmiClientKey(deviceId, serverAddr, serverPort);
         if (!controller.createClient(clientKey)) {
             log.warn("Unable to create client for {}, aborting operation", deviceId);
             return null;