only allows basic username/password config, and does not provide the
ability to set any of the other WPA options. Regardless, this is
generally sufficient to associate.
Perhaps in the future this could allow full configuring (e.g. being able
to set "anonymous identity", and perhaps some of the more obscure WPA
options), though perhaps that will better belong in bsdconfig when that
grows wlan config ability.
MFC after: 1 week
093b9154fd