Fix slowness problems
Fix slowness problems

The `get_aliases()` function was also sometimes called through
`shell.get_aliases()`.
Since the `history` rule also uses aliases, the shell was always
executed twice to get the aliases list.

nvbn/thefuck,princeofdarkness76/thefuck,manashmndl/thefuck,scorphus/thefuck,beni55/thefuck,bigplus/thefuck,redreamality/thefuck,LawrenceHan/thefuck,hxddh/thefuck,MJerty/thefuck,thinkerchan/thefuck,thinkerchan/thefuck,thesoulkiller/thefuck,Clpsplug/thefuck,levythu/thefuck,mlk/thefuck,subajat1/thefuck,scorphus/thefuck,hxddh/thefuck,BertieJim/thefuck,vanita5/thefuck,MJerty/thefuck,subajat1/thefuck,zhangzhishan/thefuck,mlk/thefuck,vanita5/thefuck,ostree/thefuck,thesoulkiller/thefuck,redreamality/thefuck,SimenB/thefuck,roth1002/thefuck,bigplus/thefuck,mcarton/thefuck,AntonChankin/thefuck,lawrencebenson/thefuck,mcarton/thefuck,princeofdarkness76/thefuck,barneyElDinosaurio/thefuck,manashmndl/thefuck,SimenB/thefuck,PLNech/thefuck,BertieJim/thefuck,ostree/thefuck,AntonChankin/thefuck,barneyElDinosaurio/thefuck,PLNech/thefuck,beni55/thefuck,levythu/thefuck,LawrenceHan/thefuck,lawrencebenson/thefuck,Clpsplug/thefuck,roth1002/thefuck,nvbn/thefuck