[FIX] sale_coupon: can duplicate sale order lines

Fix the commit a42c27f99e0061b7c4f6597e4 which inverts the initial
filter. The change remove all sale order lines for the simple order
create in the backend.

opw-1819977

models/sale_order.py

@@ -37,9 +37,8 @@ class SaleOrder(models.Model):
             order._update_existing_reward_lines()
 
     def copy(self, default=None):
-        order = super(SaleOrder, self).copy(dict(default or {}, order_line=False))
-        for line in self._get_reward_lines():
-            line.copy({'order_id': order.id})
+        order = super(SaleOrder, self).copy(default)
+        order._get_reward_lines().unlink()
         order.with_context(sale_coupon_no_loop=False)._create_new_no_code_promo_reward_lines()
         return order