command: don't update UPDATE_VIDEO options while changing file

When the current playlist entry changes, or when quitting, and
file-local options values are reset, the VO re-renders the current file
with the new option values before rendering the next file, if any,
causing flicker.

The previous commit fixed it for zoom/pan-related options. Fixing it for
options with UPDATE_VIDEO, e.g. brightness/gamma/saturation/contrast, is
much easier since we just have to ignore UPDATE_VIDEO when playback is
quitting. The only reason that flag was added is for doing something
no-osd add gamma 1 while paused (531868f), so even if we ignore it
while quitting playback, the VO will update automatically on the next
file.

Author: guidocella

player/command.c

@@ -8072,7 +8072,7 @@ void mp_option_run_callback(struct MPContext *mpctx, struct mp_option_callback *
         update_lavfi_complex(mpctx);
 
     if (flags & UPDATE_VIDEO) {
-        if (mpctx->video_out) {
+        if (mpctx->video_out && !mpctx->stop_play) {
             vo_control(mpctx->video_out, VOCTRL_UPDATE_RENDER_OPTS, NULL);
             mp_wakeup_core(mpctx);
         }