Make it less likely we will blow away ALL our backups when we retire a single host

 12. schedule a removal of the host's backup, on the backup server

     (currently `bungei`):

        echo rm -rf /srv/backups/bacula/$host/ | at now + 30 days

        echo rm -rf /srv/backups/bacula/$host.torproject.org/ | at now + 30 days

 13. if it's a physical machine or a virtual host we don't control,

     schedule removal from racks or hosts with upstream