Fix incorrect control buffer length when filling WSAMSG for WSARecvMsg

Somehow, this bug causes problems with listen sockets on Windows 11
platform.

After some number of client connections being abruptly terminated
(e.g. client has crashed), the host just stops to invoke connection
state change callbacks for the still opened listen socket.

In this particular case, `WSARecvMsg` always returns -1 (SOCKET_ERROR)
and `WSAGetLastError()` returns 10014 (WSAEFAULT), which indicates
there's a problem with function arguments.

So, it seems, that in some cases Windows will try to use the control
data, but if there's been some problem with it, the connection will
just remain in the broken state forever.

Signed-off-by: Pavel Solodovnikov <[email protected]>

Author: ManManson

src/steamnetworkingsockets/clientlib/steamnetworkingsockets_lowlevel.cpp

@@ -2373,7 +2373,7 @@ static bool DrainSocket( CRawUDPSocketImpl *pSock )
 			{
 				msg.dwBufferCount = 1;
 				msg.lpBuffers = (WSABUF *)&iov_buf;
-				msg.Control.len = sizeof(buf);
+				msg.Control.len = sizeof(buf_control);
 				msg.Control.buf = buf_control;
 				msg.dwFlags = 0;