NodeEntry
Full constructor: port of node_entry(node_id const&, udp::endpoint const&, int rtt, bool pinged).
Parameters
pinged
whether we have already had a verified response from this endpoint; if so timeoutCount starts at 0 (confirmed), otherwise at the NOT_PINGED sentinel.
Endpoint-only constructor with an unknown (all-zero) id: port of explicit node_entry(udp::endpoint const& ep). Such an entry is "not pinged" and "not verified".