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/GnmiHandshaker.java b/drivers/gnmi/src/main/java/org/onosproject/drivers/gnmi/GnmiHandshaker.java
index d1ee1b8..c443460 100644
--- a/drivers/gnmi/src/main/java/org/onosproject/drivers/gnmi/GnmiHandshaker.java
+++ b/drivers/gnmi/src/main/java/org/onosproject/drivers/gnmi/GnmiHandshaker.java
@@ -77,7 +77,9 @@
             return false;
         }
 
-        return getFutureWithDeadline(client.isServiceAvailable(), "getting availability", false);
+        return getFutureWithDeadline(
+                client.isServiceAvailable(),
+                "checking if gNMI service is available", false);
     }
 
     @Override