avformat/utils: Close codec context since it is allocated by avformat_new_stream in refrence to ticket 2716

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

libavformat/utils.c

@@ -3178,6 +3178,9 @@ void ff_free_stream(AVFormatContext *s, AVStream *st){
     av_assert0(s->nb_streams>0);
     av_assert0(s->streams[ s->nb_streams-1 ] == st);
 
+    if (st->codec) {
+        avcodec_close(st->codec);
+    }
     if (st->parser) {
         av_parser_close(st->parser);
     }