Clean up scan handling

Remove obsolete active/passive scan handling - drivers always
do active scan.

Also, remove AP_SCAN hack for preventing connections and use
the TYPE=ONLY scan.

Bug: 8158647
Change-Id: I8f70e19219ad789b7501a40529bcd6b6524739e8

Conflicts:
	services/java/com/android/server/wifi/WifiService.java
	wifi/java/android/net/wifi/WifiStateMachine.java