RFR: JDK-8318736: com/sun/jdi/JdwpOnThrowTest.java failed with "transport error 202: bind failed: Address already in use" [v6]

[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:

  Update test/jdk/com/sun/jdi/lib/jdb/Debuggee.java
  
  Co-authored-by: Alex Menkov <69548902+alexmenkov at users.noreply.github.com>

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Changes:
  - all: https://git.openjdk.org/jdk/pull/16358/files
  - new: https://git.openjdk.org/jdk/pull/16358/files/8a9b7133..8168a8ef

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=16358&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=16358&range=04-05

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 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