Fix SocketResponder on Windows

Fix SocketResponder on Windows

There seems to be a race in some tests in the System test suite that use
SocketResponder on Windows. Some tests fail with an exception that the socket
has been closed before they get a chance to see the response sent by the
SocketResponder. The same happens occasionally when using SocketResponder on
.NET. This patch changes the order of the Socket.Shutdown() calls and adds a
Socket.Receive() before Shutdown() is called to give the sender a chance to
actually send any data before the responder shuts down and closes its side of
the connection.