[jdk11u-dev] RFR: 8239785: Cgroups: Incorrect detection logic on old systems in hotspot

[Jonathan Dowland]

This is a backport of 8239785 for jdk11u. It depends upon 
pr/865: 8253714 (hopefully the bots will figure this out automatically)

It's not clean, but the only conflict was the copyright line in the
comment header for src/hotspot/share/prims/whitebox.hpp.

I tried these tests, and they pass:

    test/hotspot/jtreg/applications/ctw/modules/java_compiler.java
    test/hotspot/jtreg/compiler/c2/Test8004741.java
    test/hotspot/jtreg/containers/cgroup/CgroupSubsystemFactory.java

Awaiting tier tests via GA.

-------------

Commit messages:
 - 8239785: Cgroups: Incorrect detection logic on old systems in hotspot
 - Backport ff6843ca4842498791061f924c545fa9469cc1dc
 - Fix tests
 - Add parital 8250627 backport
 - Backport 4def210a22faaec6b47912dd314e6365ea48d28f
 - Backport d462a6b5c9bd3dae5257cca42ea38c19cb742e3c

Changes: https://git.openjdk.java.net/jdk11u-dev/pull/880/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk11u-dev&pr=880&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8239785
  Stats: 7797 lines in 46 files changed: 5404 ins; 2198 del; 195 mod
  Patch: https://git.openjdk.java.net/jdk11u-dev/pull/880.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk11u-dev pull/880/head:pull/880

PR: https://git.openjdk.java.net/jdk11u-dev/pull/880