lease: use time.Until in 'Remaining'
lease: use time.Until in 'Remaining'

Fix 'gosimple' warnings.

Signed-off-by: Gyu-Ho Lee <3454051ee3341eb69bdf6fca40899cdad4d86496@gmail.com>

whuwxl/etcd,etcd-io/etcd,bdarnell/etcd,mqliang/etcd,sebrandon1/etcd,cockroachdb/etcd,li-ang/etcd,glevand/coreos--etcd,whuwxl/etcd,akauppi/etcd,ajityagaty/etcd,YuleiXiao/etcd,etcd-io/etcd,joshix/etcd,coreos/etcd,cockroachdb/etcd,rnaveiras/etcd,ajityagaty/etcd,lorneli/etcd,mqliang/etcd,heyitsanthony/etcd,vimalk78/etcd,gyuho/etcd,a-robinson/etcd,visheshnp/etcd,ajityagaty/etcd,lorneli/etcd,visheshnp/etcd,a-robinson/etcd,rnaveiras/etcd,joshix/etcd,dannysauer/etcd,bluebreezecf/etcd,mkumatag/etcd,mickep76/etcd,YuleiXiao/etcd,gyuho/etcd,heyitsanthony/etcd,sinsharat/etcd,bluebreezecf/etcd,mqliang/etcd,fanminshi/etcd,sebrandon1/etcd,xiang90/etcd,dannysauer/etcd,glevand/coreos--etcd,xiang90/etcd,rnaveiras/etcd,sinsharat/etcd,mkumatag/etcd,bdarnell/etcd,vimalk78/etcd,akauppi/etcd,etcd-io/etcd,fanminshi/etcd,mickep76/etcd,mkumatag/etcd,coreos/etcd,li-ang/etcd