Fix processing of events when build finished.

What does this MR do?

Update pipeline after processing builds. Otherwise we can get into scenario where pipeline will be marked as running.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

This solves a quite significant regression in Pipeline processing.

Proper fix is to move all this to Sidekiq Worker and process pipeline there. I'll do it after 8.12 release.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?