avformat/hls: copy rw_timeout from parent to child AVIOContexts.
The rw_timeout option is currently not applied when opening media playlist,
segment, or encryption key URLs. This can cause the HLS demuxer to block
indefinitely, even when the rw_timeout option has been specified. This change
simply enables carrying over the rw_timeout option when the demuxer opens these
URLs.
Reviewed-by: Steven Liu <lq@chinaffmpeg.org> Signed-off-by: Richard Shaffer <rshaffer@tunein.com>