decoder: pause aout at creation in corner case (fix #6369)

If pausing the decoder races with setting up the audio output pipeline,
the decoder can end up already paused when the audio output is created.

The audio output insists on a strict start -> (pause -> resume ->)*
(pause ->)? stop series of state transition. So it must be paused
explicitly in this corner case.

I have not investigated whether this problem affects the video output
but this seems very likely too.

src/input/decoder.c

@@ -2256,6 +2256,8 @@ static aout_buffer_t *aout_new_buffer( decoder_t *p_dec, int i_samples )
 
         p_owner->p_aout = p_aout;
         DecoderUpdateFormatLocked( p_dec );
+        if( unlikely(p_owner->b_paused) ) /* fake pause if needed */
+            aout_DecChangePause( p_aout, true, mdate() );
 
         vlc_mutex_unlock( &p_owner->lock );