cvetriager: context generator: check stable kernels for patches

New functions were added to search for patches in the stable kernels.
Now additional common file was added to take care of common functions
between contextgenerator and patchapplier.

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

Change-Id: Ia3e14dbc3f4013cbbab1c239868627e116925b0d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2252062
Reviewed-by: Zubin Mithra <zsm@chromium.org>
Commit-Queue: Wanda Mora <morawand@chromium.org>
Tested-by: Wanda Mora <morawand@chromium.org>
6 files changed