Migrate OOBE configuration loading to DBus service

Fake implementation still reads configuration provided
via command line.

Bug: 854101
Change-Id: I88cb4466cbc5118218251e14b20c92f2806acf30
Reviewed-on: https://chromium-review.googlesource.com/1183497
Commit-Queue: Denis Kuznetsov <[email protected]>
Reviewed-by: Steven Bennetts <[email protected]>
Reviewed-by: Alexander Alekseev <[email protected]>
Cr-Commit-Position: refs/heads/master@{#584987}
20 files changed