cvetriager: refactoring to common.py

Completed some refactoring by moving common functionality between files
to common.py.

BUG=chromium:1093363
TEST=python setup.py test

Change-Id: I42de75e5761aaceaa2bdbb2d0d7e78c2bba5f5d4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2276099
Reviewed-by: Zubin Mithra <zsm@chromium.org>
Commit-Queue: Wanda Mora <morawand@chromium.org>
Tested-by: Wanda Mora <morawand@chromium.org>
5 files changed