cron job to clean up rabbitmq connections

Install a cleanup script to terminate RabbitMQ connections that don't
have any channels, set up a cron job to run the script every minute.

Change-Id: I1d9e79a9ef28076f83dd9426d17de7d8d4b97d30
Related-Bug: #856764
Merge "cron job to clean up rabbitmq connections" into stable/5.0