RFR: 8356658: java/foreign/TestBufferStackStress2.java failed again with junit action timed out

[Per Minborg]

This PR proposes to add a safety net around closing the executor. Apparently, in some rare configuration, the VT is not run/notified correctly.

Not completing the test for such a configuration is unlikely to mask potential issues that this test is supposed to reveal.

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Commit messages:
 - Add safety net around stalled thread

Changes: https://git.openjdk.org/jdk/pull/25177/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25177&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8356658
  Stats: 10 lines in 1 file changed: 10 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/25177.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25177/head:pull/25177

PR: https://git.openjdk.org/jdk/pull/25177