13757 Fix ConfigContext reference to DeviceType (#13804)

* 13757 do prefetch to work around Django issue with vars in init (DeviceType)

* 13757 use self.__dict to access vars in init

* 13757 change test

netbox/dcim/models/cables.py

@@ -98,10 +98,10 @@ class Cable(PrimaryModel):
         super().__init__(*args, **kwargs)
 
         # A copy of the PK to be used by __str__ in case the object is deleted
-        self._pk = self.pk
+        self._pk = self.__dict__.get('id')
 
         # Cache the original status so we can check later if it's been changed
-        self._orig_status = self.status
+        self._orig_status = self.__dict__.get('status')
 
         self._terminations_modified = False
 

netbox/dcim/models/device_component_templates.py

@@ -89,7 +89,7 @@ class ComponentTemplateModel(ChangeLoggedModel, TrackingModelMixin):
         super().__init__(*args, **kwargs)
 
         # Cache the original DeviceType ID for reference under clean()
-        self._original_device_type = self.device_type_id
+        self._original_device_type = self.__dict__.get('device_type_id')
 
     def to_objectchange(self, action):
         objectchange = super().to_objectchange(action)

netbox/dcim/models/device_components.py

@@ -86,7 +86,7 @@ class ComponentModel(NetBoxModel):
         super().__init__(*args, **kwargs)
 
         # Cache the original Device ID for reference under clean()
-        self._original_device = self.device_id
+        self._original_device = self.__dict__.get('device_id')
 
     def __str__(self):
         if self.label:

netbox/dcim/models/devices.py

@@ -205,11 +205,11 @@ class DeviceType(ImageAttachmentsMixin, PrimaryModel, WeightMixin):
         super().__init__(*args, **kwargs)
 
         # Save a copy of u_height for validation in clean()
-        self._original_u_height = self.u_height
+        self._original_u_height = self.__dict__.get('u_height')
 
         # Save references to the original front/rear images
-        self._original_front_image = self.front_image
-        self._original_rear_image = self.rear_image
+        self._original_front_image = self.__dict__.get('front_image')
+        self._original_rear_image = self.__dict__.get('rear_image')
 
     def get_absolute_url(self):
         return reverse('dcim:devicetype', args=[self.pk])