Set JUnit check to be pending before maven build starts

[timja]

I was watching this PR #3102 and it was very hard to tell what was remaining.
Hopefully this helps by making pending stages visible in GitHub.

Testing done

Copy paste from Jenkins core:
https://github.com/jenkinsci/jenkins/blob/master/Jenkinsfile#L121C13-L121C60

Submitter checklist

Beta Give feedback

1. Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
2. Ensure that the pull request title represents the desired changelog entry
3. Please describe what you did
4. Link to relevant issues in GitHub or Jira
5. Link to relevant pull requests, esp. upstream and downstream changes
6. Ensure you have provided tests - that demonstrates feature works or fixes the issue

[MarkEWaite]

Thanks.

[MarkEWaite]

I'll watch this pull request to update the weekly version:

• Update dependency org.jenkins-ci.main:jenkins-war to v2.453 #3104

When @alecharp runs the weekly release of plugin BOM at the end of this week, he'll probably need to watch it to assure no surprises from the additional information being sent to GitHub.