Description of problem:
When calculating the rates using tiers, selection of tier to be used for rating is not working properly.
As C&U data is generated hourly, when finding the tier to use it applies that to the hourly C&U data, and not to the proper amount (i.e. daily or monthly amount), thus returning a different tier than expected. 

Version-Release number of selected component (if applicable):
4.1

How reproducible:
Always

Steps to Reproduce:
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1.Define a custom tiered rate for a metric; for eg: CPU used
2.Create a chargeback report based on the tiered rate.

Actual results:
The per time is only allowed to be hourly

Expected results:
Per time should be a selection of options (hourly, daily, weekly, monthly), and rate should be applied properly

Additional info:
Original bug has additional information about the error