release: Always use NO_ROOT for distribute* and package*

We used to have two different code paths for generating release media
dist sets, one which expected to run as root, and one which did not.
It was possible that the two different paths could generate different
results.

We can use the path that does not *require* root also when running as
root, so use it always. We'll want to do eventually do the same for all
release targets, but these ones are an easy place to start.

Reviewed by: brooks
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D48041