[Forwardport] magento/magento2#10057

[namlier]

Original Pull Request

#14327

Description

Current Pull Request contains fix for issue #10057 .
Problem related to products with configured backorder.
If you place order with backorder product from frontend - everything work properly: backorder order items will have status 'Backordered'.
But when you try to place order/edit/reorder from backoffice, backorder products will not have 'Backorder' status.

Fixed Issue

1. Editing order with backordered items results in new order not correctly marking order items as backordered #10057: Editing order with backordered items results in new order not correctly marking order items as backordered.

Manual testing scenarios

Steps to reproduce

1. Set a product up as backorderable - 0 quantity stock, "allow orders below 0", in stock, enabled.
2. Go to BO -> Sales -> Operations -> Orders -> Create New Order
3. Create new order with backorderable product.
4. Check order item details which was created from backorderable product.

Expected result

1. Order item has status 'Backordered'.

Actual result

1. Order item has status 'Ordered'.

Contribution checklist

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds on Travis CI are green)