[CrOS MultiDevice] Remove cryptauth service.

Since the MultiDevice API flag has been enabled, the cryptauth service
class is no longer used.  This CL removes the class and instances
where it is called.

Bug: 912743
Change-Id: Iadcb5cd38fa70f4c4bb3d842940992faf33761af
Reviewed-on: https://chromium-review.googlesource.com/c/1367103
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Ryan Hansberry <hansberry@chromium.org>
Commit-Queue: Regan Hsu <hsuregan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616801}
28 files changed