detect_tmp_cruft: merge functionality from detect_stale_mounts

Signed-off-by: Andreas Beckmann <anbe@debian.org>
detect_tmp_cruft: move to slave-bin and run from slave crontab

this is a script for the slave

Signed-off-by: Andreas Beckmann <anbe@debian.org>
detect_slave_problems: move to slave-bin and run from slave crontab

this is a script for the slave

Signed-off-by: Andreas Beckmann <anbe@debian.org>