[jdk8u-dev] RFR: 8206456: [TESTBUG] docker jtreg tests fail on systems without cpuset.effective_cpus / cpuset.effective_mems

[Jonathan Dowland]

This is a backport of 6fc4db4799599df66a2cf5207068336ce68136ff to jdk8u-dev.

It's a test-only change, that I wish to backport as part of cgroups v2 support. Whilst not directly cgroups v2 specific, this will ease further backports by reducing merge conflicts.

The original commit touched two files: MetricsCpuTester.java and MetricsTester.java. This backport only touches MetricsCpuTester.java. The changes from the original comit to MetricsTester.java were already merged into jdk8u-dev with "8223147: JFR Backport...".

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Commit messages:
 - 8206456: [TESTBUG] docker jtreg tests fail on systems without cpuset.effective_cpus / cpuset.effective_mem

Changes: https://git.openjdk.org/jdk8u-dev/pull/123/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=123&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8206456
  Stats: 14 lines in 1 file changed: 6 ins; 0 del; 8 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/123.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev pull/123/head:pull/123

PR: https://git.openjdk.org/jdk8u-dev/pull/123