Fixes for SimExoticsTests jobs - ATLASSIM-4663

Follows on from !34869 (merged). Add back imports of units as they are used when specialConfiguration strings are evaluated. Commented these lines, so that they are ignored by the flake8 checks. Fixes ATLASSIM-4663.

While fixing this I noticed that the specialConfiguration variables in Simulation/G4Extensions/Charginos/python/CharginosConfig.py were being multiplied by units (MeV or ns) in the python code, even though they were already being specified with units in the specialConfiguration strings. (Presumably the convention changed, but the python code was not updated.) I've fixed this in master, but fortunately both MeV and ns evaluate to "1", so MC16 samples should be unaffected.