Avoid ListBuckets() call instead rely on simple HTTP GET (#8475)

This is to avoid making calls to backend and requiring
gateways to allow permissions for ListBuckets() operation
just for Liveness checks, we can avoid this and make
our liveness checks to be more performant.

cmd/gateway/hdfs/gateway-hdfs.go

@@ -227,7 +227,8 @@ func (n *hdfsObjects) StorageInfo(ctx context.Context) minio.StorageInfo {
 	}
 	sinfo := minio.StorageInfo{}
 	sinfo.Used = []uint64{fsInfo.Used}
-	sinfo.Backend.Type = minio.Unknown
+	sinfo.Backend.Type = minio.BackendGateway
+	sinfo.Backend.GatewayOnline = true
 	return sinfo
 }