Add local IPs to autodetected endpoints for a client

[sgielen]

My laptop and PC are within the same subnet. By default, if I don't pass any endpoints, their auto-detected endpoints are only their public IPs as received from our fake STUN implementation. However, they can't reach each other on their public IPs.

If I add their local IPs to their list of endpoints, they can reach each other fine. As long as each client tries all endpoints until one works, as is current behavior, this should have few downsides. At most, if someone else has another machine behind the same local IP, there may be some warnings in their logs that incorrect certificates are being used.