Changing the driver on a car shouldn't change the
fleet.vehicle.log.services associated. We should keep the driver
assigned to the car at the time the service was done.

closes odoo/odoo#54264

Taskid: 2208080
X-original-commit: 5422bb8d6e3db5d6932570116af74ea634c40a51
Signed-off-by: Paul Morelle <madprog@users.noreply.github.com>