VOL-1723 - add readiness probe capability to rw-core

Change-Id: I1cf42e88712586f140a2dfa9d0b638b48261caac
diff --git a/common/grpc/server.go b/common/grpc/server.go
index d5685f1..e3f3d99 100644
--- a/common/grpc/server.go
+++ b/common/grpc/server.go
@@ -118,7 +118,9 @@
 Stop servicing GRPC requests
 */
 func (s *GrpcServer) Stop() {
-	s.gs.Stop()
+	if s.gs != nil {
+		s.gs.Stop()
+	}
 }
 
 /*