**Impacted versions:** 8.0

**Steps to reproduce:**
To reproduce it is necessary the fifo configuration in the assignation of quants in moves.

- Create a sale order with two lines of the same product, one of that line with a route that generate moves between warehouse.

<img width="1231" alt="skitch 65" src="https://cloud.githubusercontent.com/assets/11341058/24102907/d575a638-0d53-11e7-922e-a3f034d43e94.png">

The route used has three pull rules:

1. From Stock Warehouse_1 to Virtual Locations/Inter Company Transit
2. From Virtual Locations/Inter Company Transit to Stock Warehouse_2
3. From Stock Warehouse_2 to Customers

<img width="1224" alt="skitch 66" src="https://cloud.githubusercontent.com/assets/11341058/24103147/b7c2bfbc-0d54-11e7-955c-87247a10e0bd.png">

- Confirm the sale order. It must be created three pickings:

<img width="1226" alt="skitch 67" src="https://cloud.githubusercontent.com/assets/11341058/24103498/d90c9b38-0d55-11e7-97ff-f986df8cdd9b.png">

- Transfer first two pickings.

<img width="1230" alt="skitch 70" src="https://cloud.githubusercontent.com/assets/11341058/24104496/b7b0be8a-0d58-11e7-89a2-4331fceec1d8.png">

- Before transfer third picking, review that one move has reserved the quant correctly because was reserved from the previous pickings.

<img width="1215" alt="skitch 68" src="https://cloud.githubusercontent.com/assets/11341058/24103908/23952cc8-0d57-11e7-9346-bd48d7edb54a.png">

**Current behavior:**

When check availability of this third picking, the quant already reserved is moved to the other move.

<img width="1264" alt="skitch 69" src="https://cloud.githubusercontent.com/assets/11341058/24104056/8be11616-0d57-11e7-8763-a90507315b19.png">
 
**Expected behavior:**

When check availability of this third picking, the moves already reserved must not be altered.


move_dict = prod2move_ids[product_id][index]
            qty_on_link = min(move_dict['remaining_qty'], qty_to_assign)
            self.pool.get('stock.move.operation.link').create(cr, uid, {'move_id': move_dict['move'].id, 'operation_id': operation_id, 'qty': qty_on_link, 'reserved_quant_id': quant_id}, context=context)
            if move_dict['remaining_qty'] == qty_on_link:
                prod2move_ids[product_id].pop(index)
            else:
                move_dict['remaining_qty'] -= qty_on_link
            return qty_on_link
        def _create_link_for_quant(operation_id, quant, qty):
            """create a link for given operation and reserved move of given quant, for the max quantity possible, and returns this quantity"""
            if not quant.reservation_id.id:
                return _create_link_for_product(operation_id, quant.product_id.id, qty)
            qty_on_link = 0
            for i in range(0, len(prod2move_ids[quant.product_id.id])):
                if prod2move_ids[quant.product_id.id][i]['move'].id != quant.reservation_id.id:
                    continue
                qty_on_link = _create_link_for_index(operation_id, i, quant.product_id.id, qty, quant_id=quant.id)
                break
            return qty_on_link
        def _create_link_for_product(operation_id, product_id, qty):