rc.d: add a service jails config to all base system services

This gives more permissions to services (e.g. network access to
services which require this) when they are started as an automatic
service jail.

The sshd patch is important for the sshd-related functionality as
described in the man-page in the service jails part.

The location of the added env vars is supposed to allow overriding them
in rc.conf, and to hard-disable the use of svcj for some parts where it
doesn't make sense or will not work.

Only a subset of all of the services are fully tested (I'm running this
since more than a year with various services started as service jails).
The untested parts should be most of the time ok, in some edge-cases
more permissions are needed inside the service jail.
Differential Revision: https://reviews.freebsd.org/D40371

rc: Fix quoting in the zpoolreguid script

Reported by: 0mp
Fixes: 227caacc918a ("rc: Add a zpoolreguid rc.d script")
Sponsored by: The FreeBSD Foundation

rc: Add a zpoolreguid rc.d script

If one boots up multiple copies of a template VM image containing a
zpool, the pool GUIDs will be identical, making it impossible to, e.g.,
share datasets between them.

This diff introduces a simple workaround for the problem: one can use
the script to, upon first boot, assign a new GUID to one or more zpools.
This will be useful when building ZFS-based VM images from release(7).

Reviewed by: mav, allanjude, asomers
Reviewed by: Pau Amma (docs)
MFC after: 1 month
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D35336