FairScheduler: Handle condition which can result in an infinite loop in attemptScheduling.

if (!reservationExceedsThreshold(node, type)) {
      LOG.info("Making reservation: node=" + node.getNodeName() +
              " app_id=" + getApplicationId());
      if (!alreadyReserved) {
        getMetrics().reserveResource(getUser(), container.getResource());
        RMContainer rmContainer =
                super.reserve(node, priority, null, container);
        node.reserveResource(this, priority, rmContainer);
        setReservation(node);
      } else {
        RMContainer rmContainer = node.getReservedContainer();
        super.reserve(node, priority, rmContainer, container);
        node.reserveResource(this, priority, rmContainer);
        setReservation(node);
      }
    }

      while (node.getReservedContainer() == null) {
        boolean assignedContainer = false;
        if (!queueMgr.getRootQueue().assignContainer(node).equals(
            Resources.none())) {
          assignedContainers++;
          assignedContainer = true;
          
        }
        
        if (!assignedContainer) { break; }
        if (!assignMultiple) { break; }
        if ((assignedContainers >= maxAssign) && (maxAssign > 0)) { break; }
      }