RFR: 8310525: DynamicLauncher for JDP test needs to try harder to find a free port

[Kevin Walls]

JDP tests only make 3 attempts to find a free port, using getFreePort().
We know getFreePort() is racy and you need to make sure the port really is fee when trying to use it.

Make 10 attempts.  Leave the logic unchanged.  Also fix a typo in another test.

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Commit messages:
 - 8310525: DynamicLauncher for JDP test needs to try harder to find a free port

Changes: https://git.openjdk.org/jdk/pull/20991/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20991&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/jdk/pull/20991.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20991/head:pull/20991

PR: https://git.openjdk.org/jdk/pull/20991