object: set default zone/zonegroup/realm values for external rgw

currently if multisite is not configured Rook sets values for
zone/zonegroup/realm as object store name which is only valid for
internal ceph object store. This may not exists for rgw running in
external cluster.

Signed-off-by: Jiffin Tony Thottan <thottanjiffin@gmail.com>

pkg/operator/ceph/object/objectstore.go

@@ -214,6 +214,11 @@ func getMultisiteForObjectStore(clusterdContext *clusterd.Context, spec *cephv1.
 		return realm.Name, zonegroup.Name, zone.Name, nil
 	}
 
+	// TODO: check or fix https://github.com/rook/rook/issues/9750
+	if spec.IsExternal() {
+		return "", "default", "default", nil
+	}
+
 	return name, name, name, nil
 }