Flaky portableWordCountBatch and portableWordCountStreaming tests

The tests :sdks:python:test-suites:portable:py2:portableWordCountBatch and :sdks:python:test-suites:portable:py2:portableWordCountStreaming are flaky, sometimes throws grpc errrors.

Stacktrace

!Sr5cNnx8sAW.png|width=2049,height=1001!
In text:
```

INFO:root:Using Python SDK docker image: apache/beam_python2.7_sdk:2.21.0.dev. If the image is not
available at local, we will try to pull from hub.docker.comINFO:apache_beam.runners.portability.fn_api_runner_transforms:====================
====================INFO:apache_beam.utils.subprocess_server:Starting
service with ['docker' 'run' '-v' '/usr/bin/docker:/bin/docker' '-v' '/var/run/docker.sock:/var/run/docker.sock'
'--network=host' 'apache/beam_flink1.9_job_server:latest' '--job-host' 'localhost' '--job-port' '58753'
'--artifact-port' '60175' '--expansion-port' '33067']INFO:apache_beam.utils.subprocess_server:[main]
INFO org.apache.beam.runners.fnexecution.jobsubmission.JobServerDriver - ArtifactStagingService started
on localhost:60175INFO:apache_beam.utils.subprocess_server:[main] INFO org.apache.beam.runners.fnexecution.jobsubmission.JobServerDriver
- Java ExpansionService started on localhost:33067INFO:apache_beam.utils.subprocess_server:[main] INFO
org.apache.beam.runners.fnexecution.jobsubmission.JobServerDriver - JobService started on localhost:58753ERROR:grpc._common:Exception
deserializing message!Traceback (most recent call last): File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Portable_Python_Commit/src/build/gradleenv/1866363813/local/lib/python2.7/site-packages/grpc/_common.py",
line 84, in _transform return transformer(message)DecodeError: Error parsing messageTraceback (most
recent call last): File "/usr/lib/python2.7/runpy.py", line 174, in _run_module_as_main "__main__",
fname, loader, pkg_name) File "/usr/lib/python2.7/runpy.py", line 72, in _run_code exec code in
run_globals File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Portable_Python_Commit/src/build/gradleenv/1866363813/lib/python2.7/site-packages/apache_beam/examples/wordcount.py",
line 142, in run() File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Portable_Python_Commit/src/build/gradleenv/1866363813/lib/python2.7/site-packages/apache_beam/examples/wordcount.py",
line 121, in run result = p.run() File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Portable_Python_Commit/src/build/gradleenv/1866363813/local/lib/python2.7/site-packages/apache_beam/pipeline.py",
line 495, in run self._options).run(False) File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Portable_Python_Commit/src/build/gradleenv/1866363813/local/lib/python2.7/site-packages/apache_beam/pipeline.py",
line 508, in run return self.runner.run_pipeline(self, self._options) File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Portable_Python_Commit/src/build/gradleenv/1866363813/local/lib/python2.7/site-packages/apache_beam/runners/portability/portable_runner.py",
line 401, in run_pipeline job_service_handle.submit(proto_pipeline) File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Portable_Python_Commit/src/build/gradleenv/1866363813/local/lib/python2.7/site-packages/apache_beam/runners/portability/portable_runner.py",
line 102, in submit prepare_response = self.prepare(proto_pipeline) File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Portable_Python_Commit/src/build/gradleenv/1866363813/local/lib/python2.7/site-packages/apache_beam/runners/portability/portable_runner.py",
line 179, in prepare timeout=self.timeout) File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Portable_Python_Commit/src/build/gradleenv/1866363813/local/lib/python2.7/site-packages/grpc/_channel.py",
line 826, in __call__ return _end_unary_response_blocking(state, call, False, None) File "/home/jenkins/jenkins-slave/workspace/beam_PreCommit_Portable_Python_Commit/src/build/gradleenv/1866363813/local/lib/python2.7/site-packages/grpc/_channel.py",
line 729, in _end_unary_response_blocking raise _InactiveRpcError(state)grpc._channel._InactiveRpcError:
<_InactiveRpcError of RPC that terminated with: status = StatusCode.INTERNAL details = "Exception deserializing
response!" debug_error_string = "None">

```

A gradle scan [example](https://scans.gradle.com/s/yv63cefske4cy).

Imported from Jira [BEAM-9549](https://issues.apache.org/jira/browse/BEAM-9549). Original Jira may contain additional context.
Reported by: ningk.