columnstore replication failover from master updates server-id

If you have a multi node system with replication then if UM1 is to go down then the system will automate failover to another UM, however say UM2 has it' server-id value changed to 1 from 2. This is bad and we should simply make UM2 the new master only. This will avoid problems with InnoDB replication (no impact to ColumnStore tables) Presumably this was done for a reason so should make sure that we cover this.