Hi
Set 2 Nodes in HA mode active/passive, then set the node1 as preferred master, then once everything is active... click on shutdown for the master node... then after connecting again to the webadmin click on remove node (for the node1 which had been shutdown)..
then go in configuration you will see that preferred master is set to only 1 (no name...) this should be at least reseted to none...
thx