When wpa_supplicant exits, it uses SIOCSIWMLME to request
deauthentication.  softmac then tries to reassociate without any user
intervention, which isn't the desired behaviour of this signal.

This change makes softmac only attempt reassociation if the remote
network itself deauthenticated us.
Signed-off-by: Daniel Drake <dsd@gentoo.org>
Acked-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>