PXC/Galera dashboards: Empty service name with MySQL version < 5.6.40

In all PXC dashboards, the service_name variable is being populated by the following query:

query_result(mysql_galera_variables_info{wsrep_cluster_name=~"$cluster"} * on(service_name) mysql_global_variables_wsrep_rsu_commit_timeout)

The problem is since the wsrep_rsu_commit_timeout only became available in MySQL 5.6.40, the query returns no results if the clients are running an older version.
This effectively causes no data to be displayed on the PXC dashboards.

A potential fix would be to replace that with a variable available in every version, for example:

query_result(mysql_galera_variables_info{wsrep_cluster_name=~"$cluster"} * on(service_name) mysql_global_variables_wsrep_auto_increment_control)