ServiceSingleton: Improve robustness and logging

Further clean up consistency for service changes when
the mutex is released.

Add additional logging for race detection.

Flag: EXEMPT bugfix
Test: for run in {1..100}; do (sleep 8; echo $run; adb shell pkill audioserver); done
Bug: 386871946
Change-Id: I88e62b3afd04c3733cd09ab72d284c06280f5520