message: net: check for invalid socket earlier in CConnman::AcceptConnection()
  This check is related to an `accept()` failure. So do the check earlier,
  closer to the `accept()` call.
  This will allow to isolate the `accept()`-specific code at the beginning
  of `CConnman::AcceptConnection()` and reuse the code that follows it.
diff: @@ -1010,11 +1010,17 @@ void CConnman::AcceptConnection(const ListenSocket& hListenSocket) {
  int nInbound = 0;
  int nMaxInbound = nMaxConnections - m_max_outbound;
  - if (hSocket != INVALID_SOCKET) {
  + if (hSocket == INVALID_SOCKET) {
  + const int nErr = WSAGetLastError();
  + if (nErr != WSAEWOULDBLOCK) {
  + LogPrintf("socket error accept failed: %s\n", NetworkErrorString(nErr));
  + }
  + return;
  + }
  +
  if (!addr.SetSockAddr((const struct sockaddr*)&sockaddr)) {
  LogPrintf("Warning: Unknown socket family\n");
  }
  - }
  NetPermissionFlags permissionFlags = NetPermissionFlags::PF_NONE;
  hListenSocket.AddSocketPermissionFlags(permissionFlags);
  @@ -1034,14 +1040,6 @@ void CConnman::AcceptConnection(const ListenSocket& hListenSocket) {
  }
  }
  - if (hSocket == INVALID_SOCKET)
  - {
  - int nErr = WSAGetLastError();
  - if (nErr != WSAEWOULDBLOCK)
  - LogPrintf("socket error accept failed: %s\n", NetworkErrorString(nErr));
  - return;
  - }
  -
  if (!fNetworkActive) {
  LogPrint(BCLog::NET, "connection from %s dropped: not accepting new connections\n", addr.ToString());
  CloseSocket(hSocket);
  