[SPARK-19868] conflict TasksetManager lead to spark stopped

## What changes were proposed in this pull request?

We must set the taskset to zombie before the DAGScheduler handles the taskEnded event. It's possible the taskEnded event will cause the DAGScheduler to launch a new stage attempt (this happens when map output data was lost), and if this happens before the taskSet has been set to zombie, it will appear that we have conflicting task sets.

Author: liujianhui <liujianhui@didichuxing>

Closes #17208 from liujianhuiouc/spark-19868.