Fix get-file

Created by: maxnoe

Sorry, I did not test my previous PR properly and I didn't expect it to be merged so directly. Should have made clear, that it was still untested and a draft.

The first commit contains the fix (mainly the import order seems to be important with Dirac)

The second commit changes the script to move only fully downloaded files into the directory, and do the downloading in a .incomplete subdirectory.