[FIX] stock: force recomputing transfer information on picking

When clicking on the Transfer button on a picking the packoperations should
always be recomputed.
If the pack operations are only computed the first time, the picking could be
modified (e.g. notice wrong quantity) and still display previous operations when
reloard the transfer button. opw 620636

addons/stock/wizard/stock_transfer_details.py

@@ -48,8 +48,7 @@ class stock_transfer_details(models.TransientModel):
         picking = self.pool.get('stock.picking').browse(cr, uid, picking_id, context=context)
         items = []
         packs = []
-        if not picking.pack_operation_ids:
-            picking.do_prepare_partial()
+        picking.do_prepare_partial()
         for op in picking.pack_operation_ids:
             item = {
                 'packop_id': op.id,