title: kafka loses all topics on reboot
body: <p>I'm trying out Kafka (0.8.2.1) in a VM, but am having trouble with it: though everything is fine while the machine remains on (even if I restart ZK/Kafka), if I reboot the machine (after gracefully shutting down ZK/Kafka) it seems all Kafka topics go lost.</p>
  
  <p>I'm probably missing something basic here, since this is probably not supposed to happen. What might it be?</p>
  
  <pre><code>cd /vagrant/kafka_2.11-0.8.2.1
  bin/zookeeper-server-start.sh config/zookeeper.properties
  bin/kafka-server-start.sh config/server.properties
  bin/kafka-topics.sh --create --zookeeper localhost:2181 --replication-factor 1 --partitions 10 --topic foo
  bin/kafka-topics.sh --list --zookeeper localhost:2181
  # foo
  # ^C then resume ZooKeeper, Kafka, or both
  bin/kafka-topics.sh --list --zookeeper localhost:2181
  # foo
  # ^C both, reboot machine, boot ZK/Kafka again
  bin/kafka-topics.sh --list --zookeeper localhost:2181
  # no topics
  </code></pre>