RFR 8134989/10, java/net/MulticastSocket/TestInterfaces.java failed due to unexpected IP address

[Felix Yang]

Hi there,

    please review a test patch for isolating a network configuration 
issue, which led to TestInterfaces failing from time to time.

Bug:

    https://bugs.openjdk.java.net/browse/JDK-8134989

Webrev:

    http://cr.openjdk.java.net/~xiaofeya/8134989/webrev.00/

Thanks,

Felix