**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.


res = self.on_change_tests(cr, uid, ids, product_id, product_uom_id, product_qty, context=context)
        if product_id and not product_uom_id:
            product = self.pool.get('product.product').browse(cr, uid, product_id, context=context)
            res['value']['product_uom_id'] = product.uom_id.id
        return res
    def on_change_tests(self, cr, uid, ids, product_id, product_uom_id, product_qty, context=None):
        res = {'value': {}}
        uom_obj = self.pool.get('product.uom')
        if product_id:
            product = self.pool.get('product.product').browse(cr, uid, product_id, context=context)
            product_uom_id = product_uom_id or product.uom_id.id
            selected_uom = uom_obj.browse(cr, uid, product_uom_id, context=context)
            if selected_uom.category_id.id != product.uom_id.category_id.id:
                res['warning'] = {
                    'title': _('Warning: wrong UoM!'),
                    'message': _('The selected UoM for product %s is not compatible with the UoM set on the product form. \nPlease choose an UoM within the same UoM category.') % (product.name)
                }
            if product_qty and 'warning' not in res:
                rounded_qty = uom_obj._compute_qty(cr, uid, product_uom_id, product_qty, product_uom_id, round=True)
                if rounded_qty != product_qty:
                    res['warning'] = {
                        'title': _('Warning: wrong quantity!'),
                        'message': _('The chosen quantity for product %s is not compatible with the UoM rounding. It will be automatically converted at confirmation') % (product.name)
                    }
        return res
    _columns = {
        'picking_id': fields.many2one('stock.picking', 'Stock Picking', help='The stock operation where the packing has been made', required=True),
        'product_id': fields.many2one('product.product', 'Product', ondelete="CASCADE"),  
        'product_uom_id': fields.many2one('product.uom', 'Product Unit of Measure'),
        'product_qty': fields.float('Quantity', digits_compute=dp.get_precision('Product Unit of Measure'), required=True),