fix start/end date in grib2 loader

[Synkevych]

dockerize-simflex/calculation/dw_gb.py

Line 46 in e9c9317

def download_data(start, end):

Change the way how end release date created

[Synkevych]

To fix the problem with an incorrect file(the file does not fully load) file should be loaded and then moved to the basic folder, it can prevent the error when there is no electricity.