Add global exclusion for the ROOT change of units warning printed on stderr and adapted tests

Add global exclusion for the ROOT change of units warning printed on stderr and adapted tests. Unfortunately with the verion of ROOT in LCG 100 and LCG 101, the following message:

Changing system of units to ROOT units (cm, s, GeV) Changing system of units to Geant4 units (mm, ns, MeV)

are printed on stderr causing the tests to fail. This is fixed in the current development branch but we need to hide thiose messages for the moment.