Second currency not filled correctly when adding account move lines

Using an account with second_currency in an account_move line is supposed to set the line second_currency thanks to on_change_account. This on_change is not working properly if the user doesn't change the o2m view to form.

Scenario tested on https://demo6.6.tryton.org/

1. Create an account with secondary_currency
2. Open account moves and create a new one
3. Using the default list view of lines, use the account created in a new line
4. Change to form view, second_currency of the line is empty
5. If you remove the account and set it again, the on_change will work correctly

I also think that amount_second_currency could be filled in this on_change