Remove peers from the `node_id_to_descriptor` even without init

Remove peers from the `node_id_to_descriptor` even without init

When a peer has finished the noise handshake, but has not yet
completed the lightning `Init`-based handshake, they will be
present in the `node_id_to_descriptor` set, even though
`Peer::handshake_complete()` returns false. Thus, when we go to
disconnect such a peer, we must ensure that we remove it from the
descriptor set as well.

Failing to do so caused an `Inconsistent peers set state!` panic in
the C bindings network handler.