RM fails to start when adding a queue (say root.A.A1) under a leaf queue (say root.A) with ordering policy fifo.
YARN supports fifo or fair for leaf queue and utilization or priority-utilization for parent queue. When the existing leaf queue (root.A) becomes parent queue - the ordering policy (fifo or fair) has to be unset. Else YARN RM will fail as fifo or fair is not a valid queue ordering policy for parent queue.
Similarly while removing a queue, unset ordering policy of leaf queue which converted from parent queue.