[fix] hr_recruitment:computation day_open and day_close added conditiona...

...l store and make sure that date_open and date value set

- Task: https://www.odoo.com/web#id=8298&view_type=form&model=project.task&menu_id=3942&action=327
- Pad: https://pad.odoo.com/p/r.phqFhEP0khhXgDIL