[SPARK-4067] refactor ExecutorUncaughtExceptionHandler

https://issues.apache.org/jira/browse/SPARK-4067

currently , we call Utils.tryOrExit everywhere
AppClient
Executor
TaskSchedulerImpl
It makes the name of ExecutorUncaughtExceptionHandler unfit to the real case....

Author: Nan Zhu <nanzhu@Nans-MacBook-Pro.local>
Author: Nan Zhu <nanzhu@nans-mbp.home>

Closes #2913 from CodingCat/SPARK-4067 and squashes the following commits:

035ee3d [Nan Zhu] make RAT happy
e62e416 [Nan Zhu] add some general Exit code
a10b63f [Nan Zhu] refactor