Cron not running in docker, added to supervisord config

Without this change, alertbot.pl never runs. Cron does work once it is added to the supervisor configuration, but I do get this error in cron.stderr.log: "/usr/sbin/cron: can't lock /var/run/crond.pid, otherpid may be 20: Resource temporarily unavailable" I'm not sure if it is a docker issue, or something with the cron configuration. It doesn't seem to impact anything.