chromeos_config: Use GCE_BEEFY builders by default.

Use GCE_BEEFY instead of BAREMETAL by default, but ensure that all
builders requiring VMTESTS are on BAREMETAL.

This is ignored by some waterfalls, and gives incorrect information
for the trybot waterfall (since trybots use vm_tests_override instead
of vmtests).

Also, move the CQ_MASTER to a GCE_WIMPY.

BUG=chromium:682400
TEST=run_tests

Change-Id: I57d0601a72c83e8f3b6679847096a24eddcf6bfa
Reviewed-on: https://chromium-review.googlesource.com/430193
Tested-by: Don Garrett <dgarrett@chromium.org>
Trybot-Ready: Don Garrett <dgarrett@chromium.org>
Reviewed-by: Ningning Xia <nxia@chromium.org>
Commit-Queue: Don Garrett <dgarrett@chromium.org>
4 files changed