RFR: JDK-8024675 - java/net/NetworkInterface/UniqueMacAddressesTest.java fails on Windows

[Mark Sheppard]

Hi
    please oblige and review the webrev below which addresses the issue

problem:
https://bugs.openjdk.java.net/browse/JDK-8024675

webrev:
http://cr.openjdk.java.net/~msheppar/8024675/webrev/

The test has been amended to only consider NetworkInterfaces
that are active (i.e. isUp() == true) and have a configured MAC address
when building the test's NetworkInterface list.
Previously, the test list was constructed from interface with a 
configured MAC address.
It was found during testing that some Windows configuration have tunnel
adapters configured with the same MAC address. These were found to be
inactive.
It is assumed that neither can be simultaneously active.

regards
Mark