RFR: 8277957: Add test group for IPv6 exclusive testing

[Ivan Šipka]

Adding test group for IPv6 exclusive testing.

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Commit messages:
 - 8277957: add IPv6 test group

Changes: https://git.openjdk.java.net/jdk/pull/6600/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6600&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277957
  Stats: 15 lines in 1 file changed: 14 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6600.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6600/head:pull/6600

PR: https://git.openjdk.java.net/jdk/pull/6600