Cluster names with prefix `bm-`: hcloud nodes won't join

[guettli]

... error syncing 'bm-cp-up4-md-..': failed to get instance metadata for node bm-cp-up4-md-...: failed to get instance metadata: no matching bare metal server found for node 'bm-cp-up4-md-...': server not found, requeuing

func isHCloudServerByName(name string) bool {
	return !strings.HasPrefix(name, hostNamePrefixRobot)  // hostNamePrefixRobot is "bm-"
}