[FIX] purchase: cancel a PO undo the closest picking cancellation

Usecase to reproduce:
- Set a product buy and MTO
- Create a SO with it and cancel it
- All the pickings are cancel
- Cancel the PO
- The picking that generate the PO is set to confirm
The picking should remain in cancel state

It happens because the button_cancel method still
consider the canceled moves.

This commit only modify destination moves if they still
require an action from the user.

addons/purchase/models/purchase.py

@@ -370,10 +370,11 @@ class PurchaseOrder(models.Model):
             if order.state in ('draft', 'sent', 'to approve'):
                 for order_line in order.order_line:
                     if order_line.move_dest_ids:
-                        siblings_states = (order_line.move_dest_ids.mapped('move_orig_ids')).mapped('state')
+                        move_dest_ids = order_line.move_dest_ids.filtered(lambda m: m.state not in ('done', 'cancel'))
+                        siblings_states = (move_dest_ids.mapped('move_orig_ids')).mapped('state')
                         if all(state in ('done', 'cancel') for state in siblings_states):
-                            order_line.move_dest_ids.write({'procure_method': 'make_to_stock'})
-                            order_line.move_dest_ids._recompute_state()
+                            move_dest_ids.write({'procure_method': 'make_to_stock'})
+                            move_dest_ids._recompute_state()
 
             for pick in order.picking_ids.filtered(lambda r: r.state != 'cancel'):
                 pick.action_cancel()