Fix integration test failure
Fix integration test failure

This was observed once on Travis:

    [ERROR]
    Traceback (most recent call last):
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/twisted/internet/defer.py", line 1416, in _inlineCallbacks
        result = result.throwExceptionIntoGenerator(g)
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/twisted/python/failure.py", line 512, in throwExceptionIntoGenerator
        return g.throw(self.type, self.value, self.tb)
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/test/int/test_client_integration.py", line 130, in test_send_offset_request
        [resp] = yield self.client.send_offset_request([req])
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/twisted/internet/defer.py", line 1418, in _inlineCallbacks
        result = g.send(result)
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/client.py", line 706, in send_offset_request
        returnValue(self._handle_responses(resps, fail_on_error, callback))
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/client.py", line 763, in _handle_responses
        BrokerResponseError.raise_for_errno(resp.error, resp)
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/common.py", line 311, in raise_for_errno
        raise subcls(*args)
    afkak.common.NotLeaderForPartitionError: error=6 (NOT_LEADER_FOR_PARTITION) OffsetResponse(topic=u'test_send_offset_request-BlehbfRnmi', partition=0, error=6, offsets=())
    afkak.test.int.test_client_integration.TestAfkakClientIntegration.test_send_offset_request
    ===============================================================================
    [ERROR]
    Traceback (most recent call last):
    Failure: twisted.internet.defer.TimeoutError: <afkak.test.int.test_group_integration.TestAfkakGroupIntegration testMethod=test_broker_restart> (test_broker_restart) still running at 120.0 secs
    afkak.test.int.test_group_integration.TestAfkakGroupIntegration.test_broker_restart
    ===============================================================================
    [ERROR]
    Traceback (most recent call last):
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/twisted/trial/util.py", line 276, in _runSequentially
        thing = yield d
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/_group.py", line 857, in stop
        yield super(ConsumerGroup, self).stop(errback_result=errback_result)
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/twisted/internet/defer.py", line 1418, in _inlineCallbacks
        result = g.send(result)
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/_group.py", line 285, in stop
        raise RestopError("Shutdown called on non-running coordinator")
    afkak.common.RestopError: Shutdown called on non-running coordinator
    afkak.test.int.test_group_integration.TestAfkakGroupIntegration.test_broker_restart
    ===============================================================================
    [ERROR]
    Traceback (most recent call last):
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/twisted/internet/defer.py", line 1418, in _inlineCallbacks
        result = g.send(result)
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/client.py", line 1249, in _send_request_to_coordinator
        self._handle_responses([decoded], True)
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/client.py", line 779, in _handle_responses
        self.reset_consumer_group_metadata(consumer_group)
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/client.py", line 281, in reset_consumer_group_metadata
        groups = tuple(_coerce_consumer_group(g) for g in groups)
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/client.py", line 281, in <genexpr>
        groups = tuple(_coerce_consumer_group(g) for g in groups)
      File "/home/travis/build/ciena/afkak/.tox/py27-int-snappy-murmur/lib/python2.7/site-packages/afkak/_util.py", line 56, in _coerce_consumer_group
        raise TypeError('consumer_group={!r} must be text'.format(consumer_group))
    exceptions.TypeError: consumer_group=None must be text

ciena/afkak,ciena/afkak