AudioFlinger: Update Track / Thread mutex handling

Prevent deadlock when removing track from active tracks.

Test: atest CtsMediaAudioTestCases (including AudioPlaybackCaptureTest)
Test: Spatializer playback.
Test: Duplicating playback BT/Speaker.
Bug: 314229445
Merged-In: I802759430cec782cdefba89ca2bbafb9af67588c
Change-Id: I802759430cec782cdefba89ca2bbafb9af67588c