make test more reliable by waiting for rebalance to complete
make test more reliable by waiting for rebalance to complete

wikimedia/operations-debs-python-pykafka,thedrow/samsa,wikimedia/operations-debs-python-pykafka,benauthor/pykafka,thedrow/samsa,benauthor/pykafka,thedrow/samsa,wikimedia/operations-debs-python-pykafka,benauthor/pykafka