Fix crash with engines that don't override getVoices().

The name of the voices was not normalized in getVoices(), therefore if
you use getDefaultVoiceName, that name possibly doesn't appear in
getVoices(). The framework would then run into a NullPointerException.

This was caught by the cts tests. Also added a few more log statements.

BUG: 22115315
Change-Id: I51404ddcd1bc10dd3e1ddaac410cfa9873bf1438