Please refactor the function normalize_worker_data

[tisnik]

The following part of code needs to be refactored into at least three parts:

1. fetching input data
2. processing/normalizing them
3. preparing results

f8a-stacks-report/f8a_report/report_helper.py

Line 265 in 33795db

def normalize_worker_data(self, start_date, end_date, stack_data, worker, frequency='weekly'):

Additionally I feel that the part where data is written back into the S3 should not be there - at least the function name suggests that just the 'normalization' is done, and the state of app is not changed otherwise.