http: do not print a warning message for expired cookies

libavformat prints a warning that the cookie couldn't be parsed (see
callers of parse_cookie()). This is obviously not true - it could be
parsed, but was simply ignored. Don't return an error to avoid the
warning.

libavformat/http.c

@@ -802,7 +802,7 @@ static int parse_cookie(HTTPContext *s, const char *p, AVDictionary **cookies)
             // if the cookie has already expired ignore it
             if (av_timegm(&new_tm) < av_gettime() / 1000000) {
                 av_dict_free(&new_params);
-                return -1;
+                return 0;
             }
 
             // only replace an older cookie with the same name