XAudio2: Use XAUDIO2_VOICE_NOSAMPLESPLAYED when possible.

For versions of XAudio2 with an IXAudio2SourceVoice::GetState() that offers a
flags parameter, we can use XAUDIO2_VOICE_NOSAMPLESPLAYED, since we don't
need this information in our current calls. According to MSDN, this makes the
the call about 3x faster.