message: Simplify checking of masternode.conf
  The checking of the port in masternode.conf files was overly complex.
  This simplifies it whilst maintaining that the port much match the
  default P2P port for the current network and removes the reliance on
  "magic numbers".
diff: @@ -73,6 +73,7 @@ bool CMasternodeConfig::read(std::string& strErr)
  }
  int port = 0;
  + int nDefaultPort = Params().GetDefaultPort();
  std::string hostname = "";
  SplitHostPort(ip, port, hostname);
  if(port == 0 || hostname == "") {
  @@ -82,18 +83,10 @@ bool CMasternodeConfig::read(std::string& strErr)
  return false;
  }
  - if (Params().NetworkID() == CBaseChainParams::MAIN) {
  - if (port != 51472) {
  - strErr = _("Invalid port detected in masternode.conf") + "\n" +
  - strprintf(_("Line: %d"), linenumber) + "\n\"" + line + "\"" + "\n" +
  - _("(must be 51472 for mainnet)");
  - streamConfig.close();
  - return false;
  - }
  - } else if (port == 51472) {
  - strErr = _("Invalid port detected in masternode.conf") + "\n" +
  - strprintf(_("Line: %d"), linenumber) + "\n\"" + line + "\"" + "\n" +
  - _("(51472 could be used only on mainnet)");
  + if (port != nDefaultPort) {
  + strErr = strprintf(_("Invalid port %d detected in masternode.conf"), port) + "\n" +
  + strprintf(_("Line: %d"), linenumber) + "\n\"" + ip + "\"" + "\n" +
  + strprintf(_("(must be %d for %s-net)"), nDefaultPort, Params().NetworkIDString());
  streamConfig.close();
  return false;
  }
  