Fix internal mute issues with bit-perfect playback.

When updating internal mute, it accesses the track collection, which
should be protected by the lock.
For a bit-perfect client, if it is muted internally, it is no needed to
stream it bit-perfectly.

Bug: 357786293
Test: manually
Flag: EXEMPT bugfix
Change-Id: I0c66380558da82bbe05c22c97f8532d0dae5ea59