**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.


""" Changes the state to assigned.
        @return: True
        """
        return self.write(cr, uid, ids, {'state': 'assigned'}, context=context)
    def check_tracking_product(self, cr, uid, product, lot_id, location, location_dest, context=None):
        check = False
        if product.track_all and not location_dest.usage == 'inventory':
            check = True
        elif product.track_incoming and location.usage in ('supplier', 'transit', 'inventory') and location_dest.usage == 'internal':
            check = True
        elif product.track_outgoing and location_dest.usage in ('customer', 'transit') and location.usage == 'internal':
            check = True
        if check and not lot_id:
            raise osv.except_osv(_('Warning!'), _('You must assign a serial number for the product %s') % (product.name))
    def check_tracking(self, cr, uid, move, lot_id, context=None):
        """ Checks if serial number is assigned to stock move or not and raise an error if it had to.
        """
        self.check_tracking_product(cr, uid, move.product_id, lot_id, move.location_id, move.location_dest_id, context=context)
        
    def action_assign(self, cr, uid, ids, context=None):
        """ Checks the product type and accordingly writes the state.
        """
        context = context or {}
        quant_obj = self.pool.get("stock.quant")
        to_assign_moves = set()
        main_domain = {}
        todo_moves = []