override in their sub-class; this eliminates the hack of interpreting the
EINPROGRESS return value to mean "don't do any of the normal work"
o correct active scanning so the first channel is only scanned once and so
per-channel passive mode is properly honored
o expose 802.11 FSM state names so every driver doesn't keep a private copy
o eliminate node parameter to ieee80211_begin_scan; it was not being used
a11c9a5cc2