chromeos_config: add eve to cheets boards

eve had not been added to _cheets_x86_boards and the behaviour of the
pre-cq is different. cheets boards do not currently run VMTests
because ARC++ wasn't working in VMs at one point. This has since been
fixed, but other VM-specific issues arise from time to time and it's
confusing why some boards (e.g. reef) do not run VMTests while eve
does.
This CL fixes the inconsistent behaviour between supposedly similar
boards.
Still TODO:
- update the VMTests blacklist with the real reason VMTests don't always
work (not ARC++, likely TPM2)
- remove VMTests from most boards and use dedicated VM builders

BUG=chromium:710492
BUG=chromium:710954
TEST=chromeos_config_unittest

Change-Id: I67914956f61eeaee47f79ea65952dba4922d389e
Reviewed-on: https://chromium-review.googlesource.com/490522
Commit-Ready: Nicolas Norvez <norvez@chromium.org>
Tested-by: Nicolas Norvez <norvez@chromium.org>
Reviewed-by: Bernie Thompson <bhthompson@chromium.org>
3 files changed