PVer4: Implement backoff for timeouts

If the client is timing out even after the 15 minute timeout interval,
it's a good indication that they are on a slow shared network connection
so it's best to implement backoff to allow all machines on the network
to download the update successfully.

The backoff gets reset as soon as an update downloads successfully.

Bug: 764429
Change-Id: I7df1e9519696122ae6b096d594eea0a1a241410f
TBR: lpz (since it is a minor change)
Reviewed-on: https://chromium-review.googlesource.com/666177
Commit-Queue: Varun Khaneja <vakh@chromium.org>
Reviewed-by: Jialiu Lin <jialiul@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501799}
2 files changed