ShiftFailure collapsed to Failure; new argument introduced to failure - offshift - in order to check whether the off-shift time should be counted in the MTTF

Currently implemented distributor is ERP5. See erp5_test_result from
https://github.com/erp5/erp5/tree/dream_distributor
The URL must be point to a DREAM Simulation Distributor, something like
http://localhost:55163/erp5/portal_task_distribution/dream_distributor