demux: make the cache refresh cached STREAM_CTRLs

This fixes the same symptom as the previous commit, but when the demuxer
thread is enabled. In this case, if nothing was read from the demuxer,
the STREAM_CTRLs weren't updated either. To the player, this looked like
the stream cache was never making progress, so playback was kept paused.

demux/demux.c

@@ -1105,6 +1105,7 @@ int demux_control(demuxer_t *demuxer, int cmd, void *arg)
     pthread_mutex_lock(&in->lock);
     if (!in->threading)
         update_cache(in);
+    pthread_cond_signal(&in->wakeup);
     int cr = cached_demux_control(in, cmd, arg);
     if (cr != DEMUXER_CTRL_DONTKNOW) {
         pthread_mutex_unlock(&in->lock);