[unibuild] Per model control of CQ hw tests

There were hardware provisioning issues with unified builds.  We have
since fixed this for reef-uni and added 8 snappy boards.

This change updates the config to respect the GoldenEye config to
determine which models for a given unified build should actually be
tested.

If no models are configured for presubmit testing, it will skip any
hardware testing for the given build.

BUG=chromium:752234
TEST=./chromeos_config_unittest

Change-Id: Ic91ae6a87fb75cd93ff11875418154f66277e81d
Reviewed-on: https://chromium-review.googlesource.com/619630
Commit-Ready: C Shapiro <shapiroc@google.com>
Tested-by: C Shapiro <shapiroc@google.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
4 files changed