Delayed Job with priority greater than

Allows a user to create DelayedJobBackedUp and specify if they want to find jobs with a priority greater than the given priority.

Deploy Plan
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> Does Infrastructure need to know anything special about this deploy?

Rollback Plan
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* To roll back this change, revert the merge with: `git revert -m 1 MERGE_SHA` and perform another deploy.

URLs
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> Links to bug tickets or user stories.

QA Plan
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> Fill in scenarios below. Review [QA Best Practices](https://source.sportngin.com/page/show/1227795-qa-best-practices).

Make sure the tests look okay and pass.
I'm not sure if returning false will cause this test to fail.  Typically, you use a `should*` or `asser_*` method to assert a value or state and if it doesn't match, throw an exception with semantic message.