Test boundary conditions explicitly

[stephen-soltesz]

The previous HistoricalIterator unit test expected results were not resilient to the time of day the test ran. So, just after UTC midnight the results would be different than just after UTC midnight + 12hrs.

This change updates the unit tests to use explicit times by overriding time.Now using monkey.Patch so that we can test independently of time of day. This change adds similar sequence handling to the DailyIterator unit tests also.

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This change is 

[coveralls]

Pull Request Test Coverage Report for Build 3436

• 0 of 0 changed or added relevant lines in 0 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.09%) to 74.008%

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Files with Coverage Reduction	New Missed Lines	%
job-service/iterators.go	2	97.59%
<!--	Total:	2		-->

Totals
Change from base Build 3433:	-0.09%
Covered Lines:	1623
Relevant Lines:	2193

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💛 - Coveralls