Load all topic values on values method.
Load all topic values on values method.

Without this, print_topics can end up with a list of None values, as seen in
testing a production Kafka instance with 200+ topics.

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