message: net: add I2P to the reachability map
  Update `CNetAddr::GetReachabilityFrom()` to recognize the I2P network so
  that we would prefer to advertise our I2P address to I2P peers.
diff: @@ -878,6 +878,11 @@ int CNetAddr::GetReachabilityFrom(const CNetAddr *paddrPartner) const
  case NET_IPV4: return REACH_IPV4; // Tor users can connect to IPv4 as well
  case NET_ONION: return REACH_PRIVATE;
  }
  + case NET_I2P:
  + switch (ourNet) {
  + case NET_I2P: return REACH_PRIVATE;
  + default: return REACH_DEFAULT;
  + }
  case NET_TEREDO:
  switch(ourNet) {
  default: return REACH_DEFAULT;
  