[feat](ssdp): Add ip filter callback holder (#96)
[feat](ssdp): Add ip filter callback holder (#96)

* [feat](ssdp): Add ip filter callback holder

Currently ssdp will announce all available ip addresses on the interface, which may not be what the dlna service actually wants.

The dlna service might not be listening on those addresses at all, which would mislead clients trying to establish a connection.

This commit allows to use a callback function to filter the ip addresses discovered by ssdp to decide whether to use.

* Update ssdp.go

- Modifiy new variable name to be more idiomatic.
- Fix code formatting issue.
anacrolix/dms,anacrolix/dms