net80211: improve one debug logging

When forcing DEUATH in ieee80211_sta_join1() log the current state
we are coming from as well. Note this isn't always the state we
are expecting as iv_state was updated already, so contrary to the
comment we usually do not see RUN there.
Leave a comment earlier with regards to this as well.

Sponsored by: The FreeBSD Foundation
Approved by: re (gjb)

(cherry picked from commit 453d1a90f8f46637404adc0278d6f3f068542733)
(cherry picked from commit f39c5ab3503cb963cc9f22b2bf82b5bc87a70e21)