Disable scheduler legacy mode in hlt2_pp_thor test
This is base on top of !1106 (merged) which should make sure we don't have any DVCommonBase
running in that test.
If that is the case, we can turn off the legacy_mode
of the scheduler, which means we don't go through SysExecute
anymore, avoiding the AlgExecState
Should bring a small speedup.
This is ready to be tested, but as it is based on !1106 (merged) it would have to be tested together with LHCb!3298 (merged)
cc: @sstahl