RFR: 8341310: Test containers/docker/TestJcmdWithSideCar.java fails after JDK-8327114 [v3]

[Severin Gehwolf]

> The change of [JDK-8327114](https://bugs.openjdk.org/browse/JDK-8327114) also increased test coverage. In particular, the `TestJcmdWithSideCar.java` test got enhanced to cover these cases (prior to [JDK-8327114](https://bugs.openjdk.org/browse/JDK-8327114) only case 1 was tested):
> 
> 1. Shared volumes between attachee and attacher and shared pid namespace
> 2. Shared volumes between attachee and attacher and shared pid namespace, both running with elevated privileges
> 3. Shared pid namespace between attachee and attacher only
> 4. Shared pid namespace between attachee and attacher, both running with elevated privileges
> 
> The OpenJDK attach code is able to handle cases 1 through 3 which pass, but the last case, `4`, hasn't been implemented yet when running as regular user and directing the container runtime to map the container user to that user as well. Thus, the test fails. For now I propose to disable the 4th test case. It can get re-enabled once the product code got updated to account for this case (tracked in https://bugs.openjdk.org/browse/JDK-8341349).
> 
> Thoughts? Could somebody please run this through Oracle's test system in order to see if this fixes the issue? Thank you!

Severin Gehwolf has updated the pull request incrementally with two additional commits since the last revision:

 - Revert "Improve runtime of test"
   
   This reverts commit 5b2f646c73b747f6fff364347031074d24e49822.
 - Revert "Remove the attachee container if it exists"
   
   This reverts commit ef7abf249268c30f726bee19dde3337d92c6493d.

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/21289/files
  - new: https://git.openjdk.org/jdk/pull/21289/files/ef7abf24..24a4303f

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21289&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21289&range=01-02

  Stats: 13 lines in 1 file changed: 3 ins; 10 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21289.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21289/head:pull/21289

PR: https://git.openjdk.org/jdk/pull/21289