Fix job page not loading because kuberenetes/prometheus URL is blocked

What does this MR do?

If a cluster is blocked, then we consider its prometheus as not configured (following suggestion from #202064 (comment 284172002))

Fixes error where this is causing job logs to not load (because the jobs endpoint somehow includes prometheus configuration).

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• [-] Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.