fix register variables
fix register variables

registered variables are always exists even the task is skipped.
So we can't judge if a task is skipped by if registered variable is
defined.

This path is to fix the bug in pool_names.yml
knandya/ursula,edtubillara/ursula,knandya/ursula,wupeiran/ursula,twaldrop/ursula,fancyhe/ursula,knandya/ursula,edtubillara/ursula,edtubillara/ursula,fancyhe/ursula,twaldrop/ursula,pgraziano/ursula,channus/ursula,lihkin213/ursula,ddaskal/ursula,rongzhus/ursula,ddaskal/ursula,nirajdp76/ursula,rongzhus/ursula,blueboxgroup/ursula,panxia6679/ursula,wupeiran/ursula,blueboxgroup/ursula,wupeiran/ursula,blueboxgroup/ursula,rongzhus/ursula,edtubillara/ursula,nirajdp76/ursula,rongzhus/ursula,nirajdp76/ursula,panxia6679/ursula,wupeiran/ursula,channus/ursula,panxia6679/ursula,fancyhe/ursula,twaldrop/ursula,ddaskal/ursula,twaldrop/ursula,channus/ursula,knandya/ursula,blueboxgroup/ursula,pgraziano/ursula,pgraziano/ursula,lihkin213/ursula,lihkin213/ursula,lihkin213/ursula,channus/ursula,pgraziano/ursula,panxia6679/ursula,ddaskal/ursula,fancyhe/ursula,nirajdp76/ursula