audio policy: fix VoIP audio switching from BT SCO to earpiece

commit 8f2f4e91 fixed b/188020987 but just for Cell calls.
This CL completes the fix for VoIP calls.

Bug: 188752649
Test: Cell and VoIP calls over earpiece and Bluetooth
Change-Id: I6a5563d9e802e664d4824b8f3c19a187529a17d7
(cherry picked from commit 97cec6f8)