Cluster healthcheck improvements (#10408)

- do not fail the healthcheck if heal status
  was not obtained from one of the nodes,
  if many nodes fail then report this as a
  catastrophic error.
- add "x-minio-write-quorum" value to match
  the write tolerance supported by server.
- admin info now states if a drive is healing
  where madmin.Disk.Healing is set to true
  and madmin.Disk.State is "ok"

pkg/madmin/info-commands.go

@@ -272,6 +272,7 @@ type Disk struct {
 	Endpoint        string  `json:"endpoint,omitempty"`
 	RootDisk        bool    `json:"rootDisk,omitempty"`
 	DrivePath       string  `json:"path,omitempty"`
+	Healing         bool    `json:"healing,omitempty"`
 	State           string  `json:"state,omitempty"`
 	UUID            string  `json:"uuid,omitempty"`
 	Model           string  `json:"model,omitempty"`