JDK 9 RFR of 8177564: Remove check for Windows XP and Server 2003 in java/nio/channels/DatagramChannel/NetworkConfiguration.java

[Brian Burkhalter]

Please review this test-only change at your convenience.

Issue:	https://bugs.openjdk.java.net/browse/JDK-8177564
Patch:	http://cr.openjdk.java.net/~bpb/8177564/webrev.00/

As Windows XP and Server 2003 are no longer supported by Java there is no point in checking for them in order to determine IPv6 capability.

Thanks,

Brian