"clean-room" environment used to query rc.conf(5) parameters.
This brings bsdconfig(8)'s sysrc.subr in-line with both the sysrc(8) manual
[provided by sysutils/sysrc] and sysrc(8)'s own sysrc.subr (now identical to
bsdconfig(8)'s sysrc.subr as of this patch).
Finally, this will allow a clean import of sysutils/sysrc (sans sysrc.subr,
already provided here).
Reviewed by: jilles
Approved by: adrian (co-mentor)
1f843bc059