[VECGEOM-345]; Enabling FPE in Orb.
FPE are now enabled in Orb unit test.
Previously FPEs were happening due to calculation of sqrt of negative value in MaskedAssign.
Now to avoid those FPEs Sqrt are applied only after taking the Abs of discriminant,
but assignment is done only when discriminant >= 0.
Thanks to Sandro Wenzel for the idea.