[DO NOT MERGE] Bluetooth support for Headless User

If Headless User 0 is enabled then don't launch Bluetooth until after
user has switched out of 0.  This is specifically an issue for
automotive platforms.

Bug: 118400949
Test: Boot device while headless user 0 is enabled, with a paired
Bluetooth device in a phonecall.

Change-Id: I9ea833df7ae7dc8841102ab9693f3810b31f672f
(cherry picked from commit 195a1c026fb17ab8b4fa0dd812381fe39126d213)