fix sporadic test failure.
fix sporadic test failure.

yungchin/pykafka,appsoma/pykafka,appsoma/pykafka,tempbottle/pykafka,benauthor/pykafka,yungchin/pykafka,fortime/pykafka,fortime/pykafka,aeroevan/pykafka,thedrow/samsa,wikimedia/operations-debs-python-pykafka,aeroevan/pykafka,wikimedia/operations-debs-python-pykafka,jofusa/pykafka,tempbottle/pykafka,wikimedia/operations-debs-python-pykafka,benauthor/pykafka,sammerry/pykafka,sontek/pykafka,sammerry/pykafka,thedrow/samsa,thedrow/samsa,jofusa/pykafka,sontek/pykafka,vortec/pykafka,benauthor/pykafka,vortec/pykafka