Merge pull request #3149 from nathanielmanistaatgoogle/drop-invoker

Drop invoker during test tear-down

src/python/grpcio_test/grpc_test/framework/interfaces/face/_blocking_invocation_inline_service.py

@@ -73,6 +73,7 @@ class TestCase(test_coverage.Coverage, unittest.TestCase):
 
     Overriding implementations must call this implementation.
     """
+    self._invoker = None
     self.implementation.destantiate(self._memo)
 
   def testSuccessfulUnaryRequestUnaryResponse(self):

src/python/grpcio_test/grpc_test/framework/interfaces/face/_event_invocation_synchronous_event_service.py

@@ -74,6 +74,7 @@ class TestCase(test_coverage.Coverage, unittest.TestCase):
 
     Overriding implementations must call this implementation.
     """
+    self._invoker = None
     self.implementation.destantiate(self._memo)
 
   def testSuccessfulUnaryRequestUnaryResponse(self):

src/python/grpcio_test/grpc_test/framework/interfaces/face/_future_invocation_asynchronous_event_service.py

@@ -103,6 +103,7 @@ class TestCase(test_coverage.Coverage, unittest.TestCase):
 
     Overriding implementations must call this implementation.
     """
+    self._invoker = None
     self.implementation.destantiate(self._memo)
     self._digest_pool.shutdown(wait=True)