If a node has been associated to a queue, PTL won't unassociate it when it is trying to revert to defaults. This causes PBS to return a 'Cannot delete busy object' error when PTL tries to delete non-default queues.
See the following:
2017-03-31 18:22:18,138 INFOCLI nodeA: /opt/pbs/bin/qmgr -c delete queue nodes_queue
2017-03-31 18:22:18,148 ERROR err: ['qmgr obj=nodes_queue svr=default: Cannot delete busy object', 'qmgr: Error (15027) returned from server']
2017-03-31 18:22:18,151 INFO ERROR