output/alsa: remove snd_pcm_state() check from DrainInternal()

This check was added 9 years ago in commit
4dc25d3908 to work around a dmix bug
which I assume has been fixed long ago.

Removing this fixes another corner case: if draining is requested
before the start threshold is reached, the PCM is still in
SND_PCM_STATE_PREPARED but not yet SND_PCM_STATE_RUNNING, which means
the submitted data will never be played.  This corner case is
realistic when playing songs shorter than the ALSA buffer (if the
buffer is very large).

src/output/plugins/AlsaOutputPlugin.cxx

@@ -712,11 +712,6 @@ AlsaOutput::Recover(int err) noexcept
 inline bool
 AlsaOutput::DrainInternal() noexcept
 {
-	if (snd_pcm_state(pcm) != SND_PCM_STATE_RUNNING) {
-		CancelInternal();
-		return true;
-	}
-
 	/* drain ring_buffer */
 	CopyRingToPeriodBuffer();