RFR: 7539: JDP Tests failing in VPN environments

[Johannes Bechberger]

Only run broadcasting related tests when supported.
Tested on Mac M1 with and without VPN.

-------------

Commit messages:
 - Formatting, again
 - Update copyright years
 - Use try-with-resources
 - Reformat changes
 - Only run broadcasting related tests when supported

Changes: https://git.openjdk.java.net/jmc/pull/369/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jmc&pr=369&range=00
  Issue: https://bugs.openjdk.java.net/browse/JMC-7539
  Stats: 48 lines in 3 files changed: 45 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jmc/pull/369.diff
  Fetch: git fetch https://git.openjdk.java.net/jmc pull/369/head:pull/369

PR: https://git.openjdk.java.net/jmc/pull/369