auth: refactor test to use common setup
auth: refactor test to use common setup

Refactored tests to pull common setup into a method.

bdarnell/etcd,heyitsanthony/etcd,armstrongli/etcd,fanminshi/etcd,sinsharat/etcd,jlamillan/etcd,coreos/etcd,ravigadde/etcd,glevand/coreos--etcd,gyuho/etcd,mickep76/etcd,cockroachdb/etcd,akauppi/etcd,a-robinson/etcd,bluebreezecf/etcd,dannysauer/etcd,joshix/etcd,ajityagaty/etcd,heyitsanthony/etcd,mqliang/etcd,tguangch/etcd,vimalk78/etcd,handsomesun/etcd,visheshnp/etcd,mkumatag/etcd,a-robinson/etcd,etcd-io/etcd,ajityagaty/etcd,fanminshi/etcd,tguangch/etcd,YuleiXiao/etcd,armstrongli/etcd,cockroachdb/etcd,etcd-io/etcd,ravigadde/etcd,rnaveiras/etcd,rnaveiras/etcd,sebrandon1/etcd,mickep76/etcd,bdarnell/etcd,YuleiXiao/etcd,CrazyJvm/etcd,li-ang/etcd,lorneli/etcd,mqliang/etcd,li-ang/etcd,lorneli/etcd,plasticbox/etcd,rnaveiras/etcd,lumjjb/etcd,bluebreezecf/etcd,sebrandon1/etcd,mkumatag/etcd,glevand/coreos--etcd,insequent/etcd,whuwxl/etcd,handsomesun/etcd,xiang90/etcd,mqliang/etcd,lumjjb/etcd,yudai/etcd,joshix/etcd,visheshnp/etcd,jlamillan/etcd,plasticbox/etcd,gyuho/etcd,whuwxl/etcd,vimalk78/etcd,coreos/etcd,dannysauer/etcd,sinsharat/etcd,CrazyJvm/etcd,ajityagaty/etcd,mkumatag/etcd,etcd-io/etcd,akauppi/etcd,yudai/etcd,insequent/etcd,xiang90/etcd