update_engine: Move scattering wait period store/load to PayloadState.
This is needed for decoupling the inference/use of this value from its
storing/loading, as we shift the former into the Update Manager.
BUG=chromium:384087
TEST=Unit tests.
Change-Id: I4b278dc817b6f148d5638122f934e9d1e280bfae
Reviewed-on: https://chromium-review.googlesource.com/221250
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>
5 files changed