Before this commit, Discount on SO line was never applied as '_onchange_discount' was not called. In this commit, We call the method explicitly to set a discount on SO line. Fixes https://github.com/odoo/odoo/issues/43970 closes odoo/odoo#43994 X-original-commit: 10fa3940bc7b28d20e7aac04e154fbcdfda69e56 Signed-off-by: Victor Feyens (vfe) <vfe@odoo.com>