cros_run_vm_test: log builder load/uptime stats

It is believed that VMTest banner exchange flake is associated with
builder load. This CL logs the builder load right before starting
the autotest phase of VMTest.

BUG=chromium:254166
TEST=None

Change-Id: I912780a72b3b2d66afdf627613b84e256c5f27b3
Reviewed-on: https://chromium-review.googlesource.com/172928
Tested-by: Aviv Keshet <akeshet@chromium.org>
Reviewed-by: Chris Sosa <sosa@chromium.org>
Commit-Queue: Aviv Keshet <akeshet@chromium.org>
1 file changed