[jdk21u] RFR: 8314501: Shenandoah: sun/tools/jhsdb/heapconfig/JMapHeapConfigTest.java fails

[Aleksey Shipilev]

Clean backport to fix the test failure with Shenandoah.

Additional testing:
 - [x] Test fails with Shenandoah without the fix, passes with it

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Commit messages:
 - Backport 812f475bc4ea84225e8bbb0b5a677eed0af864dd

Changes: https://git.openjdk.org/jdk21u/pull/74/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=74&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8314501
  Stats: 7 lines in 2 files changed: 1 ins; 3 del; 3 mod
  Patch: https://git.openjdk.org/jdk21u/pull/74.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/74/head:pull/74

PR: https://git.openjdk.org/jdk21u/pull/74