AudioService: fix synchronization for camera sound enforcement

Synchronize read/write of non-final variable mCameraSoundForced
  on mSettingsLock, and annotate accordingly.
The method updateRingerModeAffectedStreams() was synchronized
  on mSettingsLock, except in setRingerModeDelegate().

Test: see bug
Bug: 63388421
Change-Id: Iee8f3c31fdb4bf93b08e7f0217c1d85d80cc9180