Use NetBSD probe locations for consistency. We have submitted all
improved or missing probes, keeping them synchronized with NetBSD (our
blocklist upstream) should simplify upgrades and maintenance, as the
locations of these probes are a moving target, depending on upstream
OpenSSH changes.
Additionally, use BLACKLIST_AUTH_FAIL exclusively for now. At the time
of this commit BLACKLIST_BAD_USER, is a no-op. However, it will change
in a future upgrade.
Also, enhance blacklist notification messages for better debugging by
making them more descriptive.