leverage chromite cros_test_lib module

Use the helper modules chromite already provides to cover common testcase
issues like test setup/teardown.

BUG=chromium:340036
TEST=`./pre-upload_unittest.py` still works

Change-Id: I9aaed2b39536c17a2b2a16ae39aa5f7c32b0bc88
Reviewed-on: https://chromium-review.googlesource.com/184621
Reviewed-by: David James <davidjames@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
1 file changed