ctlv2: report unhealthy in cluster-health if any node is unavailable
ctlv2: report unhealthy in cluster-health if any node is unavailable

Fixes #8061 and #7032

mkumatag/etcd,armstrongli/etcd,etcd-io/etcd,bdarnell/etcd,joshix/etcd,a-robinson/etcd,heyitsanthony/etcd,li-ang/etcd,bluebreezecf/etcd,cockroachdb/etcd,joshix/etcd,xiang90/etcd,lorneli/etcd,visheshnp/etcd,sebrandon1/etcd,a-robinson/etcd,xiang90/etcd,sinsharat/etcd,dannysauer/etcd,visheshnp/etcd,armstrongli/etcd,mickep76/etcd,li-ang/etcd,mkumatag/etcd,sebrandon1/etcd,lorneli/etcd,mqliang/etcd,whuwxl/etcd,mickep76/etcd,mkumatag/etcd,ajityagaty/etcd,glevand/coreos--etcd,mqliang/etcd,fanminshi/etcd,whuwxl/etcd,akauppi/etcd,coreos/etcd,glevand/coreos--etcd,YuleiXiao/etcd,gyuho/etcd,vimalk78/etcd,heyitsanthony/etcd,bdarnell/etcd,etcd-io/etcd,bluebreezecf/etcd,etcd-io/etcd,gyuho/etcd,mqliang/etcd,ajityagaty/etcd,vimalk78/etcd,rnaveiras/etcd,rnaveiras/etcd,rnaveiras/etcd,cockroachdb/etcd,dannysauer/etcd,sinsharat/etcd,ajityagaty/etcd,coreos/etcd,YuleiXiao/etcd,akauppi/etcd,fanminshi/etcd