RFR: 8283279: [Testbug] Improve TestGetSwapSpaceSize [v2]

[Severin Gehwolf]

> Please review this container test improvement. The test in question only makes sense iff the total swap space size as reported by the container aware OperatingSystemMXBean is `0`. If that's not the case, then something else might be amiss, e.g. OperatingSystemMXBean reporting the host swap limits. In such a case a passing test tells us nothing. Certainly not if the
> fix from [JDK-8242480](https://bugs.openjdk.java.net/browse/JDK-8242480) is present or not.
> 
> Testing:
> - [x] Manual with and without the code fix of JDK-8242480. Still passes with the fix, and fails without. Tested the test on cgroups v1 and cgroups v2.

Severin Gehwolf has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Incorporate review feedback
 - Merge branch 'master' into test_getswapspace_improvement_8283279
 - 8283279: [Testbug] Improve TestGetSwapSpaceSize

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7854/files
  - new: https://git.openjdk.java.net/jdk/pull/7854/files/1bbb550a..891c2366

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7854&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7854&range=00-01

  Stats: 2978 lines in 116 files changed: 1986 ins; 629 del; 363 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7854.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7854/head:pull/7854

PR: https://git.openjdk.java.net/jdk/pull/7854