[FIX] account: Use CoA's currency by default on testing company

If a test is supposed to be run with the Belgium CoA, we expect the company is created by default with the EUR currency.
Before this commit, the currency of the company was replaced by the current company's one: USD (most of the time).

addons/account/tests/common.py

@@ -814,10 +814,8 @@ class AccountTestInvoicingCommon(SavepointCase):
             return account
 
         chart_template = chart_template or cls.env.company.chart_template_id
-        currency = cls.env.user.company_id.currency_id
         company = cls.env['res.company'].create({
             'name': company_name,
-            'currency_id': currency.id,
             **kwargs,
         })
         cls.env.user.company_ids |= company
@@ -825,7 +823,8 @@ class AccountTestInvoicingCommon(SavepointCase):
         chart_template.try_loading(company=company)
 
         # The currency could be different after the installation of the chart template.
-        company.write({'currency_id': kwargs.get('currency_id', currency.id)})
+        if kwargs.get('currency_id'):
+            company.write({'currency_id': kwargs['currency_id']})
 
         return {
             'company': company,