net80211: fix scanning after D5145 (PR 197498 related)

• In case, when we are doing <smth> -> INIT (FEXT_REINIT) -> <smth2>

state transition, cancel_scan() may be called in the first transition.
Reenqueue second state transition, so things will be executed in order.

• Discard any AUTH+ state transition request when INIT -> SCAN

transition is not done.

• Allow to track discarded state transitions via 'state' debugging

category.

Tested with:

• RTL8188EU, HOSTAP mode.
• RTL8188CUS, STA mode.
• Intel 3945BG, IBSS and STA modes.

PR: 197498
Approved by: adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D5482