Check for invalid queues in capacity scheduler

The ResourceManagerConf class that is being moved to the capacity scheduler of HADOOP-3445 needs to check for a queue name that is not configured in the resource-manager-conf.xml file in its APIs and fail if it is not available. This feature was originally available, but due to subsequent changes in HADOOP-3698, queues are no longer being configured as part of the mentioned configuration file. Hence we need a different mechanism to check for valid queues.