Try to use context/system class loader if the application class loader is not able to load a logging mdc class

[tobiasstadler]

What does this PR do?

Alternative to #2369

Checklist

• This is an enhancement of existing features, or a new feature in existing plugins
  • I have updated CHANGELOG.asciidoc
  • I have added tests that prove my fix is effective or that my feature works
  • Added an API method or config option? Document in which version this will be introduced
  • I have made corresponding changes to the documentation

[github-actions]

👋 @tobiasstadler Thanks a lot for your contribution!

It may take some time before we review a PR, so even if you don’t see activity for some time, it does not mean that we have forgotten about it.

Every once in a while we go through a process of prioritization, after which we are focussing on the tasks that were planned for the upcoming milestone. The prioritization status is typically reflected through the PR labels. It could be pending triage, a candidate for a future milestone, or have a target milestone set to it.

[ghost]

❕ Build Aborted

The PR is not allowed to run in the CI yet

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Reason: The PR is not allowed to run in the CI yet

• Start Time: 2022-01-27T18:07:24.195+0000

• Duration: 5 min 15 sec

• Commit: 6d50e9e

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

• run benchmark tests : Run the benchmark tests.

• run jdk compatibility tests : Run the JDK Compatibility tests.

• run integration tests : Run the Agent Integration tests.

• run end-to-end tests : Run the APM-ITs.

• run elasticsearch-ci/docs : Re-trigger the docs validation. (use unformatted text in the comment!)

[felixbarny]

Likely to be superseded by #2412

[tobiasstadler]

As #2369 also solves my problem, I am fine with closing this in favor of #2412