Merge changes from topic "apply-aosp-1209307-and-following"

* changes:
  [audiopolicy][enginebase] Fix schema verification
  Sync AUDIO_FLAG_XXX to/from string utility with enumeration
  [AudioPolicy][EngineConfigurable] Cleanup warn / error logs
  [AudioPolicy][EngineConfigurable] Fix new assistant stream regression
  [AudioPolicy][EngineConfigurable] Prevent regression on audio-base.h change