Similar to previous cronie changes, so far 'at' environment is also not
complete and only root user could trigger delayed tasks. Similar permission
changes are required for:
/etc/at.deny
/usr/bin/at
/var/spool/at/
/usr/bin/at is setgid to 'daemon', to differentiate with cronie. So move
'at' out of 'cron' (/var/spool/cron/at -> /var/spool/at)
another fix is to rename /etc/init.d/at to atd which is more widely used
in other distros (also required by LTP test cases)
