rootfs scripts should hit installer some day; the problem
is with variables (dumping 'em wholesale looks dirty,
and proxying those sort of defeats the approach)
rather than with scripts.

Until then, transform the data from the single variable
into a file containing one facility per line for
installer-1.8.31+ to consume.

As noted in the comment, these include a few quite strong ones:
- sshd(8) will only allow in "wheel" and "users" members
  by keys, no password access is allowed;
- password change even by root is subject to quality checks;
- su(8) is only useful to lower privileges and not gain those
  (so root access is available either through local console
  or via use of ssh keys).

Don't use if frowned upon.

use/control/sudo-su apparently lacked dependency on plain
use/control thus defeating the whole affair; thanks msp@
for spotting and reporting this.

TODO--, and this one was pretty expected
after the "invention" of iterators.