buffet: Rename RegisterAsync to Start

Name was confusing because Manager::RegisterAsync does
nothing related to registration.
It's regular initialization of the object.

BUG=none
TEST=FEATURES=test emerge-gizmo buffet

This reverts commit a4c8e97a077b4a94f72438c60a8db27dbaae7241.

Change-Id: I2c77d36b04d21b76aaece467846868354effc10d
Reviewed-on: https://chromium-review.googlesource.com/266027
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Vitaly Buka <vitalybuka@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
diff --git a/buffet/manager.h b/buffet/manager.h
index d21f062..6a4f88d 100644
--- a/buffet/manager.h
+++ b/buffet/manager.h
@@ -47,7 +47,7 @@
           object_manager);
   ~Manager();
 
-  void RegisterAsync(
+  void Start(
       const base::FilePath& config_path,
       const base::FilePath& state_path,
       const base::FilePath& test_definitions_path,