demux/mp4: bug fix for files with 'moov' at the end

This fixes a bug introduced with the fragmented MP4 patch.
Signed-off-by: Ilkka Ollakka <ileoo@videolan.org>

modules/demux/mp4/libmp4.c

@@ -3610,6 +3610,7 @@ MP4_Box_t *MP4_BoxGetRoot( stream_t *s )
         return p_root;
 
     p_root->i_size = stream_Size( s );
+    stream_Seek( p_stream, 0 );
     /* Get the rest of the file */
     i_result = MP4_ReadBoxContainerRaw( p_stream, p_root );