mac80211: keep auth state when assoc fails

When association fails, we should stay authenticated,
which in mac80211 is represented by the existence of
the mlme work struct, so we cannot free that, instead
we need to just set it to idle.

(Brought to you by the hacking session at Kernel Summit 2009 in Tokyo,
Japan. -- JWL)

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>