message: net: Send post-verack handshake messages at most once
diff: @@ -2472,8 +2472,9 @@ void PeerManager::ProcessMessage(CNode& pfrom, const std::string& msg_type, CDat
  // At this point, the outgoing message serialization version can't change.
  const CNetMsgMaker msgMaker(pfrom.GetCommonVersion());
  - if (msg_type == NetMsgType::VERACK)
  - {
  + if (msg_type == NetMsgType::VERACK) {
  + if (pfrom.fSuccessfullyConnected) return;
  +
  if (!pfrom.IsInboundConn()) {
  // Mark this node as currently connected, so we update its timestamp later.
  LOCK(cs_main);
  