lease: use sort.Strings instead of StringSlice
lease: use sort.Strings instead of StringSlice

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

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