[jdk21u] RFR: 8317834: java/lang/Thread/IsAlive.java timed out

[Aleksey Shipilev]

Makes the recently added test more reliable.

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Commit messages:
 - Backport 5522656af73347439eac6ecfef35d4a8f3dce77d

Changes: https://git.openjdk.org/jdk21u/pull/383/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=383&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8317834
  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u/pull/383.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/383/head:pull/383

PR: https://git.openjdk.org/jdk21u/pull/383