RFR(S) : 8180644: move jdk.testlibrary.NetworkConfiguration to the top level test library

[Igor Ignatyev]

http://cr.openjdk.java.net/~iignatyev//8180644/webrev.00/index.html
> 698 lines changed: 287 ins; 376 del; 35 mod; 

Hi all,

could you please review this patch which moves NetworkConfiguration  class to the top level test library? there were two instances of NetworkConfiguration: one in jdk testlibrary, another in java/nio/channels/DatagramChannel. they are almost identical, the only significant difference is that *interfaces methods of the latter return only the interfaces which support multicast, the former has special methods for that. NetworkConfiguration has been moved to the top level library and the tests were updated accordingly. 

webrev: http://cr.openjdk.java.net/~iignatyev//8180644/webrev.00/index.html
JBS: https://bugs.openjdk.java.net/browse/JDK-8180644
testing: affected tests, :jdk_net, :jdk_nio

Thanks,
-- Igor