Update "google-compute-engine" and "boto" package versions.

Newer "gsutil" versions expect a newer "google-compute-engine" package
version, and fail with an ImportError on "constants.py".

BUG=None
TEST=prod
  - ssh into failing bot, ran with current "gsutil.vpython", reproduced.
  - ssh into failing bot, ran with new "gsutil.vpython", fixed.
  - ssh into old GCE image, ran with new "gsutil.vpython", works.

Change-Id: Ied277b6dc1cda4bc46cc9d58a633620c055e9d7c
Reviewed-on: https://chromium-review.googlesource.com/706807Reviewed-by: Nodir Turakulov <nodir@chromium.org>
Commit-Queue: Daniel Jacques <dnj@chromium.org>