CTA2075: Synchronize dispatcher listener map

Fixed possible concurrrent modifications on the listener map in the
dispatcher by guarding the map.

Test: adb shell device_config put media_audio android.media.audio.loudness_configurator_api true
Test: atest LoudnessCodecConfiguratorTest
Bug: 312928467
Change-Id: If97dab0cff99d5adb7cf386a5d1c49379d3f3f46
1 file changed