Update CDF attribute generator unit tests

[maxinelasp]

Summary

The CDF attribute generator in cdf/cdf_attribute_manager.py needs additional unit tests. There is a start within the tests/ folder, but all the methods in cdf_attribute_manager need to be tested.

Requirements

The more specific the better.

• Write unit tests for the methods in cdf_attribute_manager that are missing
• Create a file for imap_cdf_manager and add tests specific to imap_cdf_manager.py
• If needed, expand existing unit tests
• If needed, correct or expand documentation

Related tickets

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