open_url_keepalive() unsets the options when it uses them, this
includes the offsets for the Range: header. When using the HLS
tag #EXT-X-BYTERANGE along with multiple files, the range options
must be preserved after open_url_keepalive() returns EOF so that
the new file can be opened. Failure to do this results in ignoring
the #EXT-X-BYTERANGE tag and reading the wrong bytes of the file.

To fix it, reset the options before calling io_open() following
open_url_keepalive() reaching EOF
Reviewed-by: Steven Liu <liuqi05@kuaishou.com>