Simplify code by removing error from ::GetModelId and ::GetName

Error where used when privet lived in separate process and was
possibility of request before config was available.

Change-Id: I48da2898ad4b1b703d0db2c2cdf9fcf3269b2f88
diff --git a/libweave/src/privet/cloud_delegate.h b/libweave/src/privet/cloud_delegate.h
index 5f79a6d..eb87e67 100644
--- a/libweave/src/privet/cloud_delegate.h
+++ b/libweave/src/privet/cloud_delegate.h
@@ -49,10 +49,10 @@
   };
 
   // Returns the model ID of the device.
-  virtual bool GetModelId(std::string* id, ErrorPtr* error) const = 0;
+  virtual std::string GetModelId() const = 0;
 
   // Returns the name of device.
-  virtual bool GetName(std::string* name, ErrorPtr* error) const = 0;
+  virtual std::string GetName() const = 0;
 
   // Returns the description of the device.
   virtual std::string GetDescription() const = 0;