RFR: 8346306: Unattached thread can cause crash during VM exit if it calls wait_if_vm_exited

[David Holmes]

Please review this simple fix to account for unattached threads using RawMonitors which check if the VM has exited.

Testing:
 - tiers 1-3 (sanity)

Thanks

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Commit messages:
 - 8346306: Unattached thread can cause crash during VM exit if it calls wait_if_vm_exited

Changes: https://git.openjdk.org/jdk/pull/22779/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22779&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8346306
  Stats: 13 lines in 2 files changed: 5 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/22779.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22779/head:pull/22779

PR: https://git.openjdk.org/jdk/pull/22779