[FIX] base: Changing company_id of a partner with child_ids

Steps to reproduce the bug:

- Let's consider a company partner P with company_id = A
- Let's consider an other partner C which is a child of P
- Change the company_id of P to B

Bug:

The company_id of C was not changed even if the field company_id
of C is in readonly as he has a parent.

opw:2179632

closes odoo/odoo#44061

X-original-commit: f41f7dc0f4f2a1682c6f81aba6512306ecf86067
Signed-off-by: Simon Goffin (sig) <sig@openerp.com>

odoo/addons/base/models/res_partner.py

@@ -515,6 +515,8 @@ class Partner(models.Model):
                     if len(companies) > 1 or company not in companies:
                         raise UserError(
                             ("The selected company is not compatible with the companies of the related user(s)"))
+                if partner.child_ids:
+                    partner.child_ids.write({'company_id': company.id})
         result = True
         # To write in SUPERUSER on field is_company and avoid access rights problems.
         if 'is_company' in vals and self.user_has_groups('base.group_partner_manager') and not self.env.su: