join_cluster and start_maintenance_mode are incompatible.
To make sure that only one is called when the node starts, add the MAINTENANCE option.
start_maintenance_mode sets _operation_mode to MAINTENANCE.
join_cluster sets _operation_mode to STARTING.
set_mode will result in an internal error if:
* it tries to set MAINTENANCE mode when the _operation_mode is other than NONE,
i.e. start_maintenance_mode is called after join_cluster (or it is called during
the drain, but it also shouldn't happen).
* it tries to set STARTING mode when the mode is set to MAINTENANCE,
i.e. join_cluster is called after start_maintenance_mode.
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