Scheduling the tasks which have no higher level locality first

For example:
An application has two executors: (exe1, host1), (exe2,host2).
And 3 tasks with locality: {task0, Seq(TaskLocation("host1", "exec1"))}, {task1, Seq(TaskLocation("host1", "exec1"), TaskLocation("host2"))},  {task2, Seq(TaskLocation("host2")}
If task0 is runing in exe1, when `allowedLocality` is NODE_LOCAL for exe2, it is better to schedule task2 fisrt, not task1, because task1 may be scheduled to exe1 later.