buffet: Allow configurable polling period

While here, switch to using a repeating timer, which is cleaner.

BUG=brillo:564,brillo:522
TEST=buffet_Registration passes.  Can touch the polling period config
flag and see that polling period changes.

Change-Id: I8d0cca5d38e8ba91dad1a97311cc20603e300654
Reviewed-on: https://chromium-review.googlesource.com/260920
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Vitaly Buka <vitalybuka@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
4 files changed
tree: 99375dd88a06fb70a7e44d931e15eb4b0f13546a
  1. buffet/