raft: Fix comment on TestLeaderBcastBeat
raft: Fix comment on TestLeaderBcastBeat

mkumatag/etcd,li-ang/etcd,ajityagaty/etcd,xiang90/etcd,dannysauer/etcd,etcd-io/etcd,rnaveiras/etcd,gyuho/etcd,etcd-io/etcd,etcd-io/etcd,xiang90/etcd,mqliang/etcd,rnaveiras/etcd,ajityagaty/etcd,mqliang/etcd,joshix/etcd,mqliang/etcd,dannysauer/etcd,coreos/etcd,gyuho/etcd,li-ang/etcd,coreos/etcd,ajityagaty/etcd,mkumatag/etcd,rnaveiras/etcd,joshix/etcd,mkumatag/etcd,cockroachdb/etcd,cockroachdb/etcd