Make background call screening compatible with BT

Add logic to deal with the new call states in the BT stack. Map
SIMULATED_RINGING as a ringing call and AUDIO_PROCESSING as a
non-existent call.

Also make a few fixes uncovered during manual testing.

Test: unit, manual
Bug: 140317205
Change-Id: Ie2d04b086a6dc2d6c04403a65c989f237fe07f74