Merge "Remove useless start of AudioTrack for TTS and improper volume setting....

Merge "Remove useless start of AudioTrack for TTS and improper volume setting. The AudioTrack that plays the synthesized audio data should only be started when the first synthesis request is sent, not after the initialization of the engine. The track volume should be initialized to it nominal level. Volumes above 1 do not provide amplification, so setting the volume to 2 is not necessary."