stream.hls: read and discard filtered sequences properly
stream.hls: read and discard filtered sequences properly

This fixes the phenomenon where during twitch stream prerolls,
a lot of TCP connections are opened / closed rapidly,
instead of the same one(s) being reused for sequential segments
like during normal operation.

The response data always needs to be read from the socket,
otherwise the socket cannot be reused by other HTTP requests
(hence the rapid closing/opening of connections during skipped segments)

gravyboat/streamlink,bastimeyer/streamlink,streamlink/streamlink,chhe/streamlink,gravyboat/streamlink,streamlink/streamlink,chhe/streamlink,bastimeyer/streamlink