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.

src/net.cpp

@@ -1008,11 +1008,17 @@ 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);
@@ -1032,14 +1038,6 @@ 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);