RFR: 8339787: Add some additional diagnostic output to java/net/ipv6tests/UdpTest.java

[serhiysachkov]

8339787: Add some additional diagnostic output to java/net/ipv6tests/UdpTest.java

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Commit messages:
 - 8339787: Add some additional diagnostic output to java/net/ipv6tests/UdpTest.java

Changes: https://git.openjdk.org/jdk/pull/21066/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21066&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8339787
  Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/21066.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21066/head:pull/21066

PR: https://git.openjdk.org/jdk/pull/21066