[FIX] base_address_city: avoid city_id field duplication

In base/res_partner.py, _fields_view_get calls _fields_view_get_address that could calls again
_fields_view_get in case of address_view_id is specified. That leads to issue in base_address_city
because the _fields_view_get_address method will replace two times the city field and then, we get
a view with two city_id fields.

see #16870 for screenshots

addons/base_address_city/models/res_partner.py

@@ -22,6 +22,8 @@ class Partner(models.Model):
         arch = super(Partner, self)._fields_view_get_address(arch)
         # render the partner address accordingly to address_view_id
         doc = etree.fromstring(arch)
+        if doc.xpath("//field[@name='city_id']"):
+           return arch
         for city_node in doc.xpath("//field[@name='city']"):
             replacement_xml = """
             <div>