RFR: 8361897: gc/z/TestUncommit.java fails with Uncommitted too slow

[Axel Boldt-Christmas]

This proposed change loosens the the threshold for flagging slow un-committing as an error in TestUncommit.java. Rather than requiring the un-committing be completed within 3 ZUncommitDelay, allow up to 5 ZUncommitDelay to accommodate the test being executed in environments where external factors affect whether un-committing is run as expected. 

In the observed intermittent failures, what can be seen is that the un-committer thread wakes up a significant time after the expected timeout has expired. And because we expect multiple timeouts, the accumulated extra time waiting can push the actual delay just past 3 ZUncommitDelay. Using a factor of 5 instead should remove all but the most extreme intermittent occurrences and still capture if the un-commit logic breaks completely.

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Commit messages:
 - 8361897: gc/z/TestUncommit.java fails with Uncommitted too slow

Changes: https://git.openjdk.org/jdk/pull/26536/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26536&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361897
  Stats: 9 lines in 1 file changed: 9 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/26536.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26536/head:pull/26536

PR: https://git.openjdk.org/jdk/pull/26536