Fix initialisation of NSWL1.py

Hi,

with this MR merged, the NSWL1.py jobOptions can be used again running

athena TrigT1NSW/NSWL1.py

on RDOs which contain the latest Run3 layouts (ATLAS-R3S-2021-01-00-00 or ATLAS-R3-2021-01-00-00).

CC'ing @gavner, @rozeny