[jdk21u-dev] RFR: 8310525: DynamicLauncher for JDP test needs to try harder to find a free port

[Goetz Lindenmaier]

I backport this test change as it also goes to 21.0.9-oracle

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Commit messages:
 - Backport 59407faf7b6861d142dbc3700a6fa9615567a275

Changes: https://git.openjdk.org/jdk21u-dev/pull/1795/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1795&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8310525
  Stats: 6 lines in 2 files changed: 2 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1795.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1795/head:pull/1795

PR: https://git.openjdk.org/jdk21u-dev/pull/1795