Impacted versions:
9.0, 10.0

Steps to reproduce:

Create a new database with language English by default and add a new language. Go to settings->translate->languages (in debug mode), inactive English. Go to contacts and "Create". 

Related: https://github.com/odoo/odoo/issues/3854

Current behavior:

Frontend error: Try read en_US language and add to partner, but this not are avalaible.

Expected behavior:
Change default language for all partners.

I need change the default value manually for create new partners:
```
UPDATE public.ir_values
   SET value='S''es_CO''
p1
.'
 WHERE id=1;
```

Video/Screenshot link (optional):


self.clear_caches()
        return super(Lang, self).create(vals)
    @api.multi
    def write(self, vals):
        lang_codes = self.mapped('code')
        if 'code' in vals and any(code != vals['code'] for code in lang_codes):
            raise UserError(_("Language code cannot be modified."))
        if vals.get('active') == False and self.env['res.users'].search([('lang', 'in', lang_codes)]):
            raise UserError(_("Cannot unactivate a language that is currently used by users."))
        self.clear_caches()
        return super(Lang, self).write(vals)
    @api.multi
    def unlink(self):
        for language in self:
            if language.code == 'en_US':
                raise UserError(_("Base Language 'en_US' can not be deleted!"))
            ctx_lang = self._context.get('lang')
            if ctx_lang and (language.code == ctx_lang):
                raise UserError(_("You cannot delete the language which is User's Preferred Language!"))
            if language.active:
                raise UserError(_("You cannot delete the language which is Active!\nPlease de-activate the language first."))
            self.env['ir.translation'].search([('lang', '=', language.code)]).unlink()
        self.clear_caches()
        return super(Lang, self).unlink()
    @api.multi
    def format(self, percent, value, grouping=False, monetary=False):