o change ieee80211_new_state handling to use a proper method that drivers

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