This is cleaner because, the `remote_addr` and `discovered_ip` are
related but two different things.
Within connectd and lightningd we use the peers `remote_addr` feature
to validate (and guess a port) to be used for IP discovery.
Also when a peer reports us a `remote_addr`, this is given to the plugin API
via the `peer_connected` hook. The network port here is not modified for
godd reason! This can be used i.e. to detect if we are behind a NAT.
But once lightningd figures enough peers report the same `remote_addr`,
it sets the port to the selected network and tells gossipd to use that for
`node_announcement` updates.
Hence, within gossipd, there is no (should not be) `remote_addr`.
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