[FIX] account: CoA load: only update tags in existing accounts

The intended behavior to only update tags and no other fields on existing
accounts during CoA loading was originally introduced in
https://github.com/odoo/odoo/pull/125320 and has recently been broken by commit
f2861b9d8d50 (https://github.com/odoo/odoo/pull/155256). This has been
recognized because of failing requests in the upgrade platform when it tried to
update the `code` field, which lead to excessive recomputations and in turn to
MemoryErrors.

The problem is that the tests, if the current `xmlid` constitutes a record
update or a new record[^1], need to be correct, no matter if the code above[^2]
managed to update the `xmlid` pointer or not. Thus, restore the previous logic
regarding that by only assigning the alternative record to the `account` var if
it is not None.

[^1]: https://github.com/odoo/odoo/blob/35bb495d5e5a8dac563ba4dee1702d77e4b71461/addons/account/models/chart_template.py#L312
      and
      https://github.com/odoo/odoo/blob/35bb495d5e5a8dac563ba4dee1702d77e4b71461/addons/account/models/chart_template.py#L314

[^2]: https://github.com/odoo/odoo/blob/35bb495d5e5a8dac563ba4dee1702d77e4b71461/addons/account/models/chart_template.py#L303

closes odoo/odoo#159950

X-original-commit: daa3747e94a6b7000617be91c0c33569bf3bd484
Signed-off-by: William André (wan) <wan@odoo.com>

addons/account/models/chart_template.py

@@ -335,13 +335,14 @@ class AccountChartTemplate(models.AbstractModel):
                         query = self.env['account.account']._search(self.env['account.account']._check_company_domain(company))
                         query.add_where("account_account.code SIMILAR TO %s", [f'{values["code"]}0*'])
                         accounts = self.env['account.account'].browse(query)
-                        account = accounts.sorted(key=lambda x: x.code != normalized_code)[0] if accounts else None
-                        if account:
+                        existing_account = accounts.sorted(key=lambda x: x.code != normalized_code)[0] if accounts else None
+                        if existing_account:
                             self.env['ir.model.data']._update_xmlids([{
                                 'xml_id': f"account.{company.id}_{xmlid}",
-                                'record': account,
+                                'record': existing_account,
                                 'noupdate': True,
                             }])
+                            account = existing_account
 
                     # on existing accounts, only tag_ids are to be updated using default data
                     if account and 'tag_ids' in data[model_name][xmlid]: