Make key_state->authenticated more state machine like

Make key_state->authenticated more state machine like

This order the states from unauthenticated to authenticated and also
changes the comparison for KS_AUTH_FALSE from != to >

It also add comments and documents part using the state machine
better.

Remove a now obsolete comment and two obsolete ifdefs. While
keeping the ifdef in ssl_verify would save a few bytes of code,
this is too minor to justify keeping the ifdef

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Antonio Quartulli <antonio@openvpn.net>
Message-Id: <20200709101603.11941-2-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg20258.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>