Fix calculate_storage_gb_hours

[QuanMPhm]

While testing calculate_storage_gb_hours, I realized that the default start and end arguments were not timezone aware, but the django timestamps for event times are. I've added timezone awareness to default start and end date arguments.

Also fixed s3-bucket-name cli argument name.

This is blocking nerc-project/coldfront-nerc#135

[naved001]

I realized that the default start and end arguments were not timezone aware, but the django timestamps for event times are.

So what was the impact of this?

[QuanMPhm]

@naved001 Running calculate_storage_gb_hours with all default arguments would error out, saying that it can't compare timezone aware and unaware timestamps. In effect, this bug should have had zero impact on all prior invoices, since the invoices won't be generated if this error was encountered