Don't follow BT audio changes outside of calls

When there's no Telecom call going on, don't use BRM to follow Bluetooth
audio changes -- this will interfere with other apps trying to use HFP.

Bug: 73274274
Test: unit test update, manual
Change-Id: Ia4e71fb71baafc9e9f8702ab72f803d47c37482a
9 files changed