Fix systemd-user HBAC rule
    
    2ef6e14c5a87724a3b37dd5f0817af48c4411e03 added an invalid HBAC rule that
    encoded the service wrongly.
    
    See: https://bugzilla.redhat.com/show_bug.cgi?id=1643928
    Fixes: https://pagure.io/freeipa/issue/7831
    Signed-off-by: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>