RFR: 8273216: JCMD does not work across container boundaries with Podman

[Severin Gehwolf]

Please review this test fix so as to make it work with podman too. I've tested this with podman 3.3.1 when running as regular user and when running as root. Also tested it with docker on cgroups v1 with root. I don't know how to do rootless docker testing.

Thoughts?

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Commit messages:
 - 8273216: JCMD does not work across container boundaries with Podman

Changes: https://git.openjdk.java.net/jdk/pull/5740/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=5740&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8273216
  Stats: 32 lines in 1 file changed: 16 ins; 9 del; 7 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5740.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5740/head:pull/5740

PR: https://git.openjdk.java.net/jdk/pull/5740