avcodec/avrndec: Fix memleak on error

If ff_codec_open2_recursive() fails, the already allocated
AVCodecContext leaks. Fix this by setting the FF_CODEC_CAP_INIT_CLEANUP
flag.

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
(cherry picked from commit 3c2128df7ffdb32a3ef34044f9a4c2f15dc1776f)

libavcodec/avrndec.c

@@ -171,5 +171,5 @@ AVCodec ff_avrn_decoder = {
     .close          = end,
     .decode         = decode_frame,
     .max_lowres     = 3,
-    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
+    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,
 };