clientv3/balancer: change balancer name to builder name.
clientv3/balancer: change balancer name to builder name.

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