Test: scheduler: update regression test for promotion change
    
    The promotion change in the previous commit affected an existing test for the
    better. The summary and graph output did not actually change (other than action
    IDs), just the process by which the graph was arrived, which can be summed up
    in this trace output difference:
    
    5260a5261
    > (can_be_master)       trace: galera:1 cannot be promoted: guest galera-bundle-docker-1 not allocated
    5262d5262
    < (pcmk__set_instance_roles)    info: Promoting galera:1 (Master galera-bundle-1)
    5266c5266
    < (pcmk__set_instance_roles)    info: galera-bundle-master: Promoted 2 instances of a possible 3 to master