[jdk8u-dev] RFR: 8197408: Bad pointer comparison and small cleanup in os_linux.cpp [v4]

[Jonathan Dowland]

> This is a backport of [JDK-8197408](https://bugs.openjdk.org/browse/JDK-8197408) to jdk8u-dev as part of cgroups v2. I've backported it as a pre-requisite for 8278951: containers/cgroup/PlainRead.java fails on Ubuntu 21.10 (<https://github.com/openjdk/jdk8u-dev/pull/155>)
> 
> Most of the original patch has been integrated already: I've left a whitespace change in for os_linux.cpp to hopefully avoid context problems later on. The majority of this patch is introducing the test PlainRead.java.
> 
> Not clean: test adjustments to jtreg metadata, imports, and JVM flags needed.

Jonathan Dowland has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains three commits:

 - PlainRead: ProcessBuilder: jdk8u-appropriate command line flags
 - adjust jtreg settings and imports for 8u
 - 8197408: Bad pointer comparison and small cleanup in os_linux.cpp
   
   Reviewed-by: bobv, stuefe

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Changes: https://git.openjdk.org/jdk8u-dev/pull/164/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk8u-dev&pr=164&range=03
  Stats: 82 lines in 2 files changed: 81 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/164.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev pull/164/head:pull/164

PR: https://git.openjdk.org/jdk8u-dev/pull/164