Steps to reproduce the bug:
- install mrp_workorder
- Create a new work center which will work every day from 8:00-9:00
- Create a BOM with component and operation, which takes 24 minutes in your work center
- Create 4 MO for this bom
- Set manually scheduled date > 1 MO should have a different date than others, e.g:
    - 3 MO → 01/dec/2021 08:00
    - 1 MO → 02/dec/2021 08:00
- Plan the MO which has different date than others

The ```planned_end_date``` is not calculated correctly

Current behavior before PR:
MO_1 : 01/dec/2021 08:00 → 01/dec/2021 08:24
MO_2 : 01/dec/2021 08:24 → 01/dec/2021 08:48
MO_3 : 02/dec/2021 08:00 → 02/dec/2021 08:24
MO_4 : 02/dec/2021 08:24 → 02/dec/2021 08:24

Problem
The MO_4 should only last 20 minutes, while it lasts 23 hours and 48 minutes.

opw-2648065

closes odoo/odoo#78377

Related: odoo/enterprise#21701
Signed-off-by: Rémy Voet <ryv@odoo.com>