etcdserver/api/etcdhttp: add "etcd_server_health_success/failures"
etcdserver/api/etcdhttp: add "etcd_server_health_success/failures"

Signed-off-by: Gyuho Lee <0fbd30d364d71722b926950b451cecd97b54fc29@amazon.com>

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