pre-upload: migrate to using cros_build_lib.RunCommand()

BUG=None
TEST=`./pre-upload_unittest.py` passes.
TEST=Tried repo upload with various commits containing unformatted
files/missing BUG=/TEST= lines. pre-upload caught all instances.

Change-Id: Ice63640c5cc80aebdb01984eb934590e517b6647
Reviewed-on: https://chromium-review.googlesource.com/291415
Commit-Ready: Rahul Chaudhry <rahulchaudhry@chromium.org>
Tested-by: Rahul Chaudhry <rahulchaudhry@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed