CLEANUP: haload: factor out two more duplicated -ee blocks

CLEANUP: haload: factor out two more duplicated -ee blocks

hld_usr_schedule() and hld_rate_task() had the same four lines
to reset a thread's rate history on a new -ee ramp generation. Move
this into hld_thr_sync_ramp_gen().

hld_usr_schedule() and the budget check added to hld_usr_task() had
the same throttle max computation. Move this into
hld_thr_rate_max(), built on top of hld_thr_rate_share().