[SPARK-13887][PYTHON][TRIVIAL][BUILD] Make lint-python script fail fast

## What changes were proposed in this pull request?

Change lint python script to stop on first error rather than building them up so its clearer why we failed (requested by rxin). Also while in the file, remove the commented out code.

## How was this patch tested?

Manually ran lint-python script with & without pep8 errors locally and verified expected results.

Author: Holden Karau <holden@us.ibm.com>

Closes #11898 from holdenk/SPARK-13887-pylint-fast-fail.