The "add-proxy" and "remove-proxy" handlers in mod_cluster subsystem do not update the persistent configuration

The mod_cluster subsystem includes handlers for "add-proxy" and "remove-proxy" that AFAICT update the runtime state that is reflected in configuration's the "proxy-list" attribute. But the "proxy-list" is not updated. The result is the configuration model will not be in sync with the runtime service and any change will be lost after restart.