peerd: Use D-Bus codegen to create correct handler for ExposeService

Use the new annotation to mark ExposeService as a handler that takes
the raw D-Bus message which it can then use to extract the sender's
unique name.

BUG=brillo:346
TEST=`FEATURES=test emerge-link peerd`

Change-Id: I176864f347eae7b39201bf23f1eadbcc7bbd52f5
Reviewed-on: https://chromium-review.googlesource.com/252322
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
4 files changed