RFR: JDK-8234935: JdwpListenTest.java and JdwpAttachTest.java getting bind failures on Windows 2016 hosts

[Alex Menkov]

Hi all,

Please review the fix for
https://bugs.openjdk.java.net/browse/JDK-8234935
webrev:
http://cr.openjdk.java.net/~amenkov/jdk15/JdwpTestsTeredo/webrev/

The failures are caused by Teredo clients 
(https://en.wikipedia.org/wiki/Teredo_tunneling).
The fix filters out corresponding addresses.

JdwpListenTest and JdwpAttachTest use the same way to get addresses for 
testing. As this is not the 1st time the algorithm is updated I decided 
to deduplicate the code and move shared code to new base class.
So actual change is the addition of

71  // Teredo clients cause intermittent errors on listen ("bind failed")
72  // and attach ("no route to host").
73  // Teredo is supposed to be a temporary measure, but some test 
machines have it.
74   if (isTeredo(addr6)) {
75    continue;
76  }

and isTeredo method implementation.

--alex