This commit fixes a memleak in the hls muxer when one uses a single file
as output. It has been forgotten to free the temporary buffers used to write
the packets so that the size of the leaks basically amounts to the size
of the output file. This commit adds the necessary free.
Reviewed-by: Steven Liu <lq@onvideo.cn>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>