[jdk17u] RFR: 8273614: Shenandoah: intermittent timeout with ConcurrentGCBreakpoint tests

[Zhengyu Gu]

I would like to backport this Shenandoah specific patch to fix intermittent timeout of a couple of tests that use concurrent GC breakpoints, due to a race condition.

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Commit messages:
 - Backport 3f07337722a0c8c6b452a44745598268d67c0864

Changes: https://git.openjdk.java.net/jdk17u/pull/200/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u&pr=200&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273614
  Stats: 27 lines in 1 file changed: 15 ins; 3 del; 9 mod
  Patch: https://git.openjdk.java.net/jdk17u/pull/200.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u pull/200/head:pull/200

PR: https://git.openjdk.java.net/jdk17u/pull/200