AURORA-480: Fix the end-to-end test

use pants_support_baseurls instead of pants_support_baseurl
incorporate fix from AURORA-523
add git clean -fdx so that we don't pull up the wrong pants.pex

Testing Done:
mba=aurora=; ./src/test/sh/org/apache/aurora/e2e/test_end_to_end.sh

Bugs closed: AURORA-480

Reviewed at https://reviews.apache.org/r/22896/