authpolicy: Add retries for kinit after domain join

The first device policy fetch after joining Active Directory can be very
slow because machine credentials need to propagate through the AD
deployment.  In that situation, retry kinit up to 60 times.

BUG=chromium:682641
TEST=manual

Change-Id: I11b4687a999d1d810744751aafb1057ef46dc6a1
Previous-Reviewed-on: https://chromium-review.googlesource.com/430754
(cherry picked from commit 2e96ab4e56b7907e3dd5c4b011da553a96beef54)
Reviewed-on: https://chromium-review.googlesource.com/430695
Tested-by: Thiemo Nagel <tnagel@chromium.org>
Trybot-Ready: Thiemo Nagel <tnagel@chromium.org>
Reviewed-by: Roman Sorokin <rsorokin@chromium.org>
Commit-Queue: Thiemo Nagel <tnagel@chromium.org>
2 files changed