storage: add dev_num parameter to Disk.create()

circle/storage/models.py

@@ -278,7 +278,7 @@ class Disk(TimeStampedModel):
 
         return Disk.create(base=self, datastore=self.datastore,
                            name=self.name, size=self.size,
-                           type=new_type)
+                           type=new_type, dev_num=self.dev_num)
 
     def get_vmdisk_desc(self):
         """Serialize disk object to the vmdriver.