Give kafka slightly longer to come up

Should reduce spurious failures where the cluster just isn't ready yet - I wish
there was a better way to actually *ask* the cluster that.

vagrant/create_topics.sh

@@ -2,7 +2,7 @@
 
 set -ex
 
-sleep 10
+sleep 12
 
 cd ${KAFKA_INSTALL_ROOT}/kafka-6667
 bin/kafka-topics.sh --create --partitions 1 --replication-factor 3 --topic single_partition --zookeeper localhost:2181