If a bootstrap fails at some stage and leaves a rabbitmq_data
container on a host, it will not bootstrap again and rabbitmq
fails to start due to root permissions on /var/lib/rabbitmq.
This patch improves the check for a valid, existing
rabbitmq_data
Closes-Bug: #1490602
Change-Id: I6a00aaef38b4ab6a60dcfb5ed2f808513b9f8c84
77466a292d