Use cros_logging instead of cros_build_lib.Warning

Replace all instances of cros_build_lib.Warning with
cros_logging.warning in crostestutils.

BUG=brillo:600
TEST=trybot

Change-Id: Iac63e2d75c8b8174af77ef0fbc318be238b7957e
Reviewed-on: https://chromium-review.googlesource.com/262229
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Ralph Nathan <ralphnathan@chromium.org>
Trybot-Ready: Ralph Nathan <ralphnathan@chromium.org>
Tested-by: Ralph Nathan <ralphnathan@chromium.org>
3 files changed