[FIX] google_account: no access error when token refresh fails

Before this fix, when a refresh of the google token was triggered
and error 400 where returned, if the user did not have write rights
on res_users, an access rights was raised

Now, the write is done and the real error is raised for the client.

Part of OPW-2123045 (needed to further investigations)

closes odoo/odoo#41651

Signed-off-by: Richard Mathot (rim) <rim@openerp.com>