ffmpeg: disable autoinsertion for -async on the output side of the filtergraph.

This fixes the issue that since the last merge -async caused 2 aresample
filters to be inserted
users that generate funny timestamps in a filtergraph should probably
manually insert a aresample filter where they need it.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

ffmpeg.c

@@ -1063,7 +1063,7 @@ static int configure_output_audio_filter(FilterGraph *fg, OutputFilter *ofilter,
     pad_idx = 0;                                                            \
 } while (0)
 
-    if (audio_sync_method > 0) {
+    if (audio_sync_method > 0 && 0) {
         char args[256] = {0};
 
         av_strlcatf(args, sizeof(args), "min_comp=0.001:min_hard_comp=%f", audio_drift_threshold);