etcdctl: don't ask password twice for etcdctl endpoint health --cluster
etcdctl: don't ask password twice for etcdctl endpoint health --cluster

Current etcdctl endpoint health --cluster asks password twice if auth
is enabled. This is because the command creates two client instances:
one for the purpose of checking endpoint health and another for
getting cluster members with MemberList(). The latter client doesn't
need to be authenticated because MemberList() is a public RPC. This
commit makes the client with no authed one.

Fix https://github.com/coreos/etcd/issues/9094

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