Remove bogus vlc_object_wait (no condition to wait on)

N.B.: libvlc snapshots remain seriously broken.
Vout is not locked when shooting. Variables are not safely set.
Vout thread does not access request field safely.
Multiple requests are not safe either. I probably missed some other
issues.

src/control/mediacontrol_audio_video.c

@@ -92,7 +92,6 @@ mediacontrol_snapshot( mediacontrol_Instance *self,
 
     vlc_object_lock( p_cache );
     vout_Control( p_vout, VOUT_SNAPSHOT );
-    vlc_object_wait( p_cache );
     vlc_object_release( p_vout );
 
     p_snapshot = ( snapshot_t* ) p_cache->p_private;