[FIX] stock: service lines duplication when grouping DO invoices

This is possible that changes happen
during the loop in the multiple pickings:
an update in a picking could update another
picking. The browse must therefore be done
inside the loop to update the pickings with
the latest changes.

Fixes odoo#4201

addons/stock/stock.py

@@ -1132,7 +1132,9 @@ def action_invoice_create(self, cr, uid, ids, journal_id=False,
         invoices_group = {}
         res = {}
         inv_type = type
-        for picking in self.browse(cr, uid, ids, context=context):
+        for picking_id in ids:
+            # The browse inside the loop is done on purpose, as a change in the pickings during the loop is possible
+            picking = self.browse(cr, uid, picking_id, context=context)
             if picking.invoice_state != '2binvoiced':
                 continue
             partner = self._get_partner_to_invoice(cr, uid, picking, context=context)