[SPARK-3293] yarn's web show "SUCCEEDED" when the driver throw a exception in yarn-client

Better not to catch `Throwable`, and don't set `exitCode` to -1 (in the shell, that translates to an exit code of 255, which is generally interpreted to mean different things than just "process exited" [1].)

[1] Some discussion: http://en.wikipedia.org/wiki/Exit_status