gce_au_worker: Revise gce_au_worker based on the new GCE util
All changes include:
* Update gce_au_worker.py with the lately added GCE Python API based utility,
i.e., gce.py, see CL:300202.
* Use locally built GCE tarball instead of depending on its existence in the
archive GCS bucket, see CL:300315.
* Update lib/constants with the credentials of the GCE project used for testing.
Background: brbug.com/1199 and crbug.com/526292.
* Handle test failures by archiving GCE tarball and test private key for repro.
* Add a unit test for gce_au_worker.py.
TEST=Trybot run with a config that enables gce tests.
Commit-Ready: Daniel Wang <email@example.com>
Tested-by: Daniel Wang <firstname.lastname@example.org>
Reviewed-by: Simran Basi <email@example.com>
5 files changed