[FIX] web: Modify existing sales order lines

Steps to reproduce:

- Create a sale order and add sale order lines(Not Inline) without saving the sale order.
- Edit any of the existing sale order line and hit on "Save & New" on the sale order line.
- Add another sale order line and hit on "Save & Close"

Bug:

A validation error was raised.

opw:1829723

addons/web/static/src/js/views/form_relational_widgets.js

@@ -1118,6 +1118,11 @@ var One2ManyListView = X2ManyListView.extend({
                     self.x2m.reload_current_view();
                 });
             },
+            create_function: function(data, options) {
+                return self.x2m.data_create(data, options).done(function() {
+                    self.x2m.reload_current_view();
+                });
+            },
             alternative_form_view: self.x2m.field.views ? self.x2m.field.views.form : undefined,
             parent_view: self.x2m.view,
             child_name: self.x2m.name,