[jdk16] RFR: 8257468: runtime/whitebox/TestWBDeflateIdleMonitors.java fails with Monitor should be deflated.: expected true to equal false

[Daniel D.Daugherty]

This is a trivial test fix to add a retry loop to the code that exercises the
WhiteBox deflateIdleMonitors() API. The failure reported in JDK-8257468
has only been seen one time in a Same-Binary-Run. I have not seen this
failure in my lab with my stress testing nor has it been seen in Mach5.

Tested with the modified test.

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Commit messages:
 - 8257468: runtime/whitebox/TestWBDeflateIdleMonitors.java fails with Monitor should be deflated.: expected true to equal false

Changes: https://git.openjdk.java.net/jdk16/pull/67/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk16&pr=67&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257468
  Stats: 18 lines in 1 file changed: 15 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk16/pull/67.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk16 pull/67/head:pull/67

PR: https://git.openjdk.java.net/jdk16/pull/67