arc: Extend StartArcInstanceRequest for skip_packages_cache_setup

This adds extra field skip_packages_cache_setup to
StartArcInstanceRequest in order to be able to skip initial packages
cache setup for autotest.

BUG=b:70511735
TEST=cheets_CacheValidationServer passes on eve/veyron_minnie

Change-Id: I25ea5f6d655200dee23ecd57b10d5de2a52deb50
Reviewed-on: https://chromium-review.googlesource.com/848418
Commit-Ready: Yury Khmel <khmel@google.com>
Tested-by: Yury Khmel <khmel@google.com>
Reviewed-by: Luis Hector Chavez <lhchavez@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
1 file changed