buffet: Refetch access token when expired.

BUG=chromium:420580
TEST=cros_workon_make buffet --test&&manual

Change-Id: I17c5eb2ef86991baed1a700007a11537bb07104d
Reviewed-on: https://chromium-review.googlesource.com/224940
Tested-by: Anton Muhin <antonm@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Anton Muhin <antonm@chromium.org>
2 files changed
tree: 7697c0583b87dd7f76c6ea604f951fa0cfa5fade
  1. buffet/