api/v3election: error on missing "leader" field
api/v3election: error on missing "leader" field

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

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