[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....
Ah nevermind - there is already UncaughtExceptionHandler