Pass ssh private key when calling cros_run_vm_update script

This also ensures that the update_engine is started before calling
image_to_live.sh. This is done as a prerequisite for enabling the
SimpleTestUpdateAndVerify for lakitu builds.

BUG=b:27858147
TEST=manually run cros_au_test_harness that later calls cros_run_vm_update

Change-Id: Ic7bb5557af3e705d83e2149e7383d5867bc4e969
Reviewed-on: https://chromium-review.googlesource.com/360633
Commit-Ready: Roberta Dobrescu <rdob@google.com>
Tested-by: Roberta Dobrescu <rdob@google.com>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Reviewed-by: Dan Shi <dshi@google.com>
2 files changed