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.cc b/buffet/manager.cc
index 00c5ad2..34dad7a 100644
--- a/buffet/manager.cc
+++ b/buffet/manager.cc
@@ -45,11 +45,11 @@
 Manager::~Manager() {
 }
 
-void Manager::RegisterAsync(const base::FilePath& config_path,
-                            const base::FilePath& state_path,
-                            const base::FilePath& test_definitions_path,
-                            bool xmpp_enabled,
-                            const AsyncEventSequencer::CompletionAction& cb) {
+void Manager::Start(const base::FilePath& config_path,
+                    const base::FilePath& state_path,
+                    const base::FilePath& test_definitions_path,
+                    bool xmpp_enabled,
+                    const AsyncEventSequencer::CompletionAction& cb) {
   command_manager_ =
       std::make_shared<CommandManager>(dbus_object_.GetObjectManager());
   command_manager_->SetOnCommandDefChanged(