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.

packages/TtsService/jni/android_tts_SynthProxy.cpp

@@ -230,9 +230,8 @@ class SynthProxyJniStorage {
               mAudioOut = NULL;
             } else {
               //LOGI("AudioTrack OK");
-              mAudioOut->setVolume(2.0f, 2.0f);
-              mAudioOut->start();
-              LOGV("AudioTrack started");
+              mAudioOut->setVolume(1.0f, 1.0f);
+              LOGV("AudioTrack ready");
             }
         }
 };