RFR(XS) : 8182672: Java 8u121 on Linux intermittently returns null for MAC address

[Seán Coffey]

Looking to backport this to jdk8u-dev. There was a minor tweak in the 
testcase around how the interfaces are streamed. As a result, I'm 
carrying out a code review for the backport. Dropped use of 
"NetworkInterface.networkInterfaces();"

Presume it's ok  :
http://cr.openjdk.java.net/~coffeys/webrev.8182672.8u-dev/webrev/

https://bugs.openjdk.java.net/browse/JDK-8182672

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Regards,
Sean.