cbuildbot: reject private CLs in the CQ

We don't want to merge CLs marked private in the CQ (pre-cq is fine),
so reject ones that are still marked as private.

BUG=chromium:825407
TEST=precq passes

Change-Id: If09243920c08f2ff505801d43f84353ff2259184
Reviewed-on: https://chromium-review.googlesource.com/1117908
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
2 files changed