Cross section mismatch in pp_tt012j (P2_gu_ttxgu) in CI tmad tests - reset_cumulative_variable was called twice in fortran and once in cudacpp

[valassi]

There is a cross section mismatch in pp_tt012j in CI tmad tests.

This only appears after fixing the rotxxx crash (which otherwise hides it).
I have seen this in the CI for PR #857, where volatile is added to fix rotxxx.
https://github.com/madgraph5/madgraph4gpu/actions/runs/9694817881/job/26753418805

*** (2-none) Compare MADEVENT_CPP xQUICK xsec to MADEVENT_FORTRAN xsec ***

ERROR! xsec from fortran (0.82047507505698292) and cpp (0.67821465194602271) differ by more than 3E-13 (0.1733878669026967)

[valassi]

I forgot to mention: the CI now runs tmad tests in each P* subprocess. The issue appears in P2_gu_ttxgu. (Other subprocesses succeed).