Properly compare job/task state enums in JobHelper.check_current_job()

[DrChat]

Summary of the Pull Request

JobHelper.check_current_job() currently always reports a successful status because it compares state enums with string literals, which will never succeed (confusingly).
In addition, by default self.onefuzz.tasks.list will only list active tasks (excluding ones that are in a shutting down state).

PR Checklist

• Applies to work item: #xxx
• CLA signed. If not, go over here and sign the CLI.
• Tests added/passed
• Requires documentation to be updated
• I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

Info on Pull Request

This simply removes string literal comparisons in favor of lists returned by the state object itself.

Validation Steps Performed

Unsure - I don't know if there's any commands that can easily be ran to check this functionality.
This should be a simple enough code review.

[Porges]

Will merge after validation run.

[Porges]

Thanks for the contribution, @DrChat!