Get object from same database we wrote it to.

This is just being really explicit about using the same db to get the
related UprnToCouncil object, that we've written to. We seem to be
hitting race conditions, and getting 'RelatedObjectDoesNotExist' errors.
This should fix that.

polling_stations/apps/data_importers/management/commands/import_eoni.py

@@ -285,8 +285,9 @@ def assign_or_remove_left_over_addresses(self):
             )
             if len(others_in_postcode) == 1:
                 other_address = others_in_postcode[0]
-                other_uprn = other_address.uprntocouncil
-                other_uprn.refresh_from_db(using=DB_NAME)
+                other_uprn = UprnToCouncil.objects.using(DB_NAME).get(
+                    uprn=other_address.uprn
+                )
                 self.stdout.write(
                     f"Updating UprnToCouncil record for {address.uprn} with gss {other_uprn.lad}"
                 )