fix flaky behavior in FakeLatencyTracker

LatencyTrackerTest exposed a race condition leading to deadlock in
FakeLatencyTracker.

This also fixes users of FakeLatencyTracker like
SoundTriggerMiddlewareLoggingTest

Bug: 275113847
Test: atest LatencyTrackerTest --iterations 20
Test: atest FakeLatencyTrackerTest --iterations 20
Test: atest SoundTriggerMiddlewareLoggingTest --iterations 20
Change-Id: I5e4a4e489711fff05c2fceffbe76c258a54cd49f