QUdpSocket spurious readyRead signals when sending datagrams on Windows Desktop

Since the QTBUG-46552 fix a trivial UDP socket client has spurious readyRead signals when writeDatagram is called. Calling hasPendingDatagrams in the signal handler returns true but in fact an error WSAECONNREST is being detected. This code is not an error as documented by Micorsoft. It occurs because the datagram is written to a port on the local host where there is no server listening which is a perfectly valid scenario.

Demo application attached.