[3200] fix for stability issue in ofagent connection manager

Change-Id: I8993eaafb7363fa9433c55b4cdec0c93450472d8
diff --git a/ofagent/connection_mgr.py b/ofagent/connection_mgr.py
index 9ccf115..11bc0c0 100644
--- a/ofagent/connection_mgr.py
+++ b/ofagent/connection_mgr.py
@@ -24,6 +24,8 @@
 from common.utils.consulhelpers import get_endpoint_from_consul
 from structlog import get_logger
 import grpc
+from grpc import StatusCode
+from grpc._channel import _Rendezvous
 from ofagent.protos import third_party
 from protos import voltha_pb2
 from grpc_client import GrpcClient
@@ -131,6 +133,10 @@
                                                        device.datapath_id))
                 returnValue(devices)
 
+            except _Rendezvous, e:
+                if e.code() == StatusCode.UNAVAILABLE:
+                    os.system("kill -15 {}".format(os.getpid()))
+
             except Exception as e:
                 log.error('Failure to retrieve devices from '
                                'voltha: {}'.format(repr(e)))