check_added_files needs to be less strict

It seems that check_added_files doesn't allow to add common fragments to new DSID directories:

https://gitlab.cern.ch/atlas-physics/pmg/mcjoboptions/-/jobs/5255146

$ source scripts/check_added_files.sh
Find files that have been added in last commit...
ERROR: file: 421xxx/421121/Pythia8_i/Pythia8_ShowerWeights.py not in white list
OK: file: 421xxx/421121/mc16.PhPy8EG_A14_ttbar_hdamp172p5_nonallhad.py in white list
ERROR: file: 421xxx/421122/Pythia8_i/Pythia8_ShowerWeights.py not in white list
OK: file: 421xxx/421122/mc16.PhPy8EG_AZNLOCTEQ6L1_Wplusenu.py in white list
OK: file: 421xxx/421123/mc16.MGPy8EvtGen_aQGCFS0_50_ZZjj_llqq.py in white list