Fix TTS regression, TTS#stop can result in #onDone callback.

Regressinon in the L, side effect of the rewrite. In pre-L android,
UtteranceProgressListener#onDone was called (but only if client
received UtteranceProgressListener#onStart for the utterance in progress)
after client called TextToSpeech#stop. This changeset reinstates
this behaviour.
+ Removed not used fallback callback

Bug: 16149006
Change-Id: I2eb5ede0abe6f5717b07f09adad861465575c238