RFR: JDK-8318736: com/sun/jdi/JdwpOnThrowTest.java failed with "transport error 202: bind failed: Address already in use" [v5]

[Johannes Bechberger]

> Fix race condition in debugger port selection, introduced with [JDK-8317920](https://bugs.openjdk.org/browse/JDK-8317920).
> 
> Tested on my Mac M1, but it doesn't contain platform-dependent code.

Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:

  Refactor as requested

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/16358/files
  - new: https://git.openjdk.org/jdk/pull/16358/files/8788131e..8a9b7133

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16358&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16358&range=03-04

  Stats: 36 lines in 1 file changed: 14 ins; 16 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/16358.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16358/head:pull/16358

PR: https://git.openjdk.org/jdk/pull/16358