New packages are built using SHA256 as instance ID (instead of SHA1).

R=iannucci@chromium.org
BUG=821194, 867819, 813782

Change-Id: I61cf71386975725f7f63097eeb62f094ff50e396
Reviewed-on: https://chromium-review.googlesource.com/1165598Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Vadim Shtayura <vadimsh@chromium.org>