Add a delay between immediate CryptAuth v2 re-enrollment attempts

Add a five-minute delay between immediate-retry attempts in the
CryptAuth v2 Enrollment scheduler. It is probably a good idea to wait a
short amount of time before retrying a failed enrollment attempt;
otherwise, we might burn through all allotted "immediate" retry attempts
specified by CryptAuth because of a transient failure.

Also, CryptAuth throttles SyncKeys requests if more than one is sent
within a five-minute window.

Bug: 899080
Change-Id: Ie8d39b5e9d5af4464ac93200508b680e7039014c
Reviewed-on: https://chromium-review.googlesource.com/c/1495739
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Josh Nohle <nohle@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636559}
2 files changed