LeAudioService: Fix crash on Airplane mode on

Fix race which cause the crash

  at com.android.bluetooth.le_audio.LeAudioService$AudioManagerRemoveAudioDeviceCallback.onAudioDevicesRemoved(LeAudioService.java:899)
  at android.media.AudioManager$NativeEventHandlerDelegate$1.handleMessage(AudioManager.java:8560)
  at android.os.Handler.dispatchMessage(Handler.java:106)
  at android.os.Looper.loopOnce(Looper.java:201)
  at android.os.Looper.loop(Looper.java:288)
  at android.app.ActivityThread.main(ActivityThread.java:7868)
  at java.lang.reflect.Method.invoke(Native Method)
  at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:936)

Bug: 262180035
Test: compile
Tag: #feature
Change-Id: I9786d38f702086c93cc852b5500f160318d4d70a