ffserver: Fix another memory leak

Don't allocate st->codec, it will be overwritten by the memcpy a few
lines further down.

Fix by Howard Chu, hyc at highlandsun dot com

Originally committed as revision 23291 to svn://svn.ffmpeg.org/ffmpeg/trunk

ffserver.c

@@ -3381,7 +3381,6 @@ static int rtp_new_av_stream(HTTPContext *c,
     st = av_mallocz(sizeof(AVStream));
     if (!st)
         goto fail;
-    st->codec= avcodec_alloc_context();
     ctx->nb_streams = 1;
     ctx->streams[0] = st;