SEBA-345: Upgrade to current gRPC and Protobuf libs

Change-Id: I7167a0a490e38cb40b8bd37da81bf78a8e3a86ea
diff --git a/ofagent/grpc_client.py b/ofagent/grpc_client.py
index f4fc6df..a1678c5 100644
--- a/ofagent/grpc_client.py
+++ b/ofagent/grpc_client.py
@@ -27,8 +27,9 @@
 from twisted.internet import threads
 from twisted.internet.defer import inlineCallbacks, returnValue, DeferredQueue
 
-from protos.voltha_pb2 import ID, VolthaLocalServiceStub, FlowTableUpdate, MeterModUpdate, \
+from protos.voltha_pb2 import ID, FlowTableUpdate, MeterModUpdate, \
     FlowGroupTableUpdate, PacketOut
+from protos.voltha_pb2_grpc import VolthaLocalServiceStub
 from protos.logical_device_pb2 import LogicalPortId
 from google.protobuf import empty_pb2