If master does not have replication settings, i.e. slave slave status is "Empty set", the attempt to make it as co-master with the slave fails with the error:

ChangeMasterTo: Cannot change master on: master1:3306 because replication is running

As far as I understand it fails in ChangeMasterCredentials function, checking whether replication is stopped or not:

	if !instance.ReplicationThreadsStopped() {
		return instance, fmt.Errorf("ChangeMasterTo: Cannot change master on: %+v because replication is running", *instanceKey)
	}

But replication is neither stopped nor running. I suppose, it is "ReplicationThreadStateNoThread".
PS: this is latest version 3.0.14 issue.