ScanOnlyModeManager: send scan available broadcast

As ScanOnlyMode transitions between idle and active, send the scan
available broadcast to WifiScanner.

Bug: 32659843
Test: frameworks/opt/net/wifi/tests/wifitests/runtests.sh
Change-Id: Id7c51901d7412b4594de9b39fabc1ffffe33d842
3 files changed