Change the defaults for portmap, sendmail and inetd to be not running them.
Make sysinstall override this on install, so the effective behavioural
change for a newly installed system is null. Overall, this makes a system
with an empty /etc/rc.conf not run any network services, and makes the
FreeBSD-provided network services that are running visible in /etc/rc.conf
(instead of making people look through /etc/defaults/rc.conf to find the
things they need to disable to secure the system.)

Reviewed by: jhb
Discussed with: The usual cabal