Back out the automatic pkg.conf installpath changes; because pkg_add has

Back out the automatic pkg.conf installpath changes; because pkg_add has
an immature heuristic for "what is a release and what is a snapshot".
This change maybe improved the post-release experience, but it damages the
pre-release experience, which may result in less effective pre-release
testing, which risks creating poor releases, which may result in poor
post-release experiences.
Specific case: subtle breakage to fw_update.