Add yarn command to list all queues

we need a yarn command to list all leaf queues.

especially in large scale cluster ,there are a large amount of  queues in tree-format for various apps , we actually need a list-all-leaf-queues interface to get queues infomation immediately ,other than search in fair scheduler.xml or in yarn-scheduler web layer by layer.sometimes we should also vertify a new queue is successfully added in scheduer, instead of fail for some format error or other wise.