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/dbus_bindings/org.chromium.Buffet.Manager.xml b/buffet/dbus_bindings/org.chromium.Buffet.Manager.xml
index ff73108..2e23802 100644
--- a/buffet/dbus_bindings/org.chromium.Buffet.Manager.xml
+++ b/buffet/dbus_bindings/org.chromium.Buffet.Manager.xml
@@ -43,20 +43,17 @@
       <tp:docstring>
         State of Buffet's cloud registration.
         Possible values include:
+          "unconfigured": Buffet has no credentials, either from an out of box
+                          state, or because device was unregistered.
 
-        "offline": Buffet has credentials, but no connectivity to the Internet.
-        "cloud_error": Buffet has credentials, but cannot contact cloud services
-                       to verify their validity.  This could indicate that cloud
-                       services are down, or that DNS is not resolving.
-        "invalid_credentials": Buffet has credentials, but they are no longer
-                               valid.
-        "unregistered": Buffet has no credentials, either from an out of
-                        box state, or because those credentials have been
-                        rejected by the cloud service.  Note that we
-                        can unregistered with or without Internet connectivity.
-        "registering": Buffet has been provided with credentials, and is
-                       registering with the cloud.
-        "registered": Buffet is online and registered with cloud services.
+          "connecting": Buffet is registered and attempting to connect to the
+                        cloud.
+
+          "connected": Buffet is online and connected to the cloud. Note that
+                       only this state requires internet connectivity.
+
+          "invalid_credentials": Buffet has credentials, but they are no longer
+                                 valid.
       </tp:docstring>
     </property>
   </interface>