RFR[8250889]: 'Disable testing SendReceiveMaxSize with preferIPv4Stack=true on the old impl until JDK-8250886 is fixed'

[Patrick Concannon]

Hi,

Could someone please review my fix for JDK-8250889 — 'Disable testing SendReceiveMaxSize with preferIPv4Stack=true on the old impl until JDK-8250886 is fixed’ ?

The `test java/net/DatagramSocket/SendReceiveMaxSize` is currently failing when run with `-Djdk.net.usePlainDatagramSocketImpl` and `-Djava.net.preferIPv4Stack=true`. This fix removes these run settings from the test until a more permanent solution can be found. 

issue: https://bugs.openjdk.java.net/browse/JDK-8250889
webrev: http://cr.openjdk.java.net/~pconcannon/8250889/webrevs/webrev.00/

Kind regards,
Patrick