Steps to reproduce:
1. Open SampleScene from attached project "AudioSourceBug.zip"
2. Open Profiler and press Record
3. Press Play
4. Find: PlayerLoop -> PostLateUpdate.UpdateAudio -> AudioManager.Update -> AudioSource.Update

Expected result: there are only 2 calls, Time ms is 0.01
Actual result: there are 6002 calls, which include non playing AudioSources, Time ms is ~0.50

Reproducible: 2018.2.0a6, 2018.2.16f1, 2018.3.0b10, 2019.1.0a8
Not reproducible: 2017.4.15f1, 2018.1.9f2, 2018.2.0a5

Note: since 2018.2.0a4 the Time ms increased to ~0.50 (even though in previous versions it was 0.01) but Calls stay at 2 (or sometimes drop to 1)