benjaminp and HyukjinKwon [SPARK-23522][PYTHON] always use sys.exit over builtin exit
The exit() builtin is only for interactive use. applications should use sys.exit().

## What changes were proposed in this pull request?

All usage of the builtin `exit()` function is replaced by `sys.exit()`.

## How was this patch tested?

I ran `python/run-tests`.

Please review http://spark.apache.org/contributing.html before opening a pull request.

Author: Benjamin Peterson <benjamin@python.org>

Closes #20682 from benjaminp/sys-exit.
Latest commit 7013eea Mar 8, 2018