Make unicorn_workers to return meaningful results

What does this MR do?

This make unicorn_workers to return correct result. It is possible as we run in master process of Unicorn which has up-to date information about running workers.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/63659

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Code review guidelines
• Merge request performance guidelines
• Style guides