privetd: Async peerd calls

PeerdClient state does not depend on any results of peerd dBus calls so can
be easily switched to async version.

BUG=brillo:285
TEST=manual, check if mDns still works with "avahi-browse -r _privet._tcp"

Change-Id: I23e8282500443195a8ca6ff97c81b2a7efceb933
Reviewed-on: https://chromium-review.googlesource.com/254724
Tested-by: Vitaly Buka <vitalybuka@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
2 files changed