Take TextToSpeechSettings out of endless loop

Launching an Activity using startActivityForResult() every time
you are in onResume() is a recipe for endless looping. I.e. every
time the launched Activity finishes it will be relaunched because
the launching Activity reenters onResume().

This change keeps the GetSampleText activity from being launched
from onResume if we already have the sample text and the Locale
hasn't changed since the last onResume.

Fixes bug 15951054.

Change-Id: I65d9070df93396d8d3a45a6673ae56826f418122