keep car proxy focus for loss always

- adding external flag check is just hiding problems
  when vehicle hal is handling focus in wrong way.
- For focus loss, keep car proxy focus. This will no
  longer hide wrong focus loss in flow like radio gaining focus back.
- also fix broken audio focus tests due to muting / unmuting

bug: 28122287
Change-Id: I16a9f5a108f3907fe718dee3ef260f3f75ac6991
3 files changed