buffet: Update RegistrationStatus enum and how it's set

Motivation is to simplify states and make them more consistent with Privet
state.

Also update buffet code that switches states to better match cloud connection
state.

CQ-DEPEND=CL:260680
BUG=brillo:572,brillo:571,brillo:592
TEST=manual, register device, restart buffet and privetd, reboot router
     checking if gcd.status of privet/info is correct.

Change-Id: I74c36d57a2396660417bf6db8166f90263d6636d
Reviewed-on: https://chromium-review.googlesource.com/260302
Tested-by: Vitaly Buka <vitalybuka@chromium.org>
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
diff --git a/buffet/registration_status.h b/buffet/registration_status.h
index eee0c81..6b75f4d 100644
--- a/buffet/registration_status.h
+++ b/buffet/registration_status.h
@@ -11,11 +11,9 @@
 
 // See the DBus interface XML file for complete descriptions of these states.
 enum class RegistrationStatus {
-  kOffline,  // We have credentials but are offline.
-  kCloudError,  // We're online, but can't talk to cloud services.
-  kUnregistered,  // We have no credentials.
-  kRegistering,  // We've just been given credentials.
-  kRegistered,  // We're registered and online.
+  kUnconfigured,        // We have no credentials.
+  kConnecting,          // We have credentials but not yet connected.
+  kConnected,           // We're registered and connected to the cloud.
   kInvalidCredentials,  // Our registration has been revoked.
 };