avformat/http: dont fail with unknown Content-Encodings

Fixes: http://m1.file.xiami.com/282/23282/343749/1769075752_709488_l.mp3

Based-on-patch-by: Crossle Song <sxm@yixia.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/http.c

@@ -437,7 +437,6 @@ static int process_line(URLContext *h, char *line, int line_count,
                 // the header at all if this is the case).
             } else {
                 av_log(h, AV_LOG_WARNING, "Unknown content coding: %s\n", p);
-                return AVERROR(ENOSYS);
             }
         }
     }