RFR: 8335124: com/sun/management/ThreadMXBean/ThreadCpuTimeArray.java failed with CPU time out of expected range

[Kevin Walls]

This test has had occasional failures for years, possibly forever.
A previous update made the test "othervm" which removed some interruptions, but a time accounting problem remains.

This change adds a simple sleep after observing that the test threads are all sleeping.

The idea is that threads may not have actually started sleeping when we observe their java.lang.Thread.State as WAITING, they may use some CPU time after that in order to actually get to sleep.

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Commit messages:
 - 8335124: com/sun/management/ThreadMXBean/ThreadCpuTimeArray.java failed with CPU time out of expected range

Changes: https://git.openjdk.org/jdk/pull/19924/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19924&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8335124
  Stats: 3 lines in 1 file changed: 2 ins; 1 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/19924.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19924/head:pull/19924

PR: https://git.openjdk.org/jdk/pull/19924