chromite: Disable vm_tests_override for lakitu paladin builders

So that trybots for them won't run the TRADITIONAL_VM_TESTS_SUPPORTED
set that includes cros_vm_test. It doesn't run on lakitu boards.

Context:
https://groups.google.com/a/google.com/d/msg/chromeos-infra-discuss/Hcoq4JfCuBU/lk0Yy0lnBQAJ

BUG=None
TEST=runtest and trybot for lakitu-paladin should not run cros_vm_test.

Change-Id: I210f6ee7e578c8a1d2f66567bd2c3547a003db38
Reviewed-on: https://chromium-review.googlesource.com/480987
Commit-Ready: Daniel Wang <wonderfly@google.com>
Tested-by: Daniel Wang <wonderfly@google.com>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
2 files changed