[FIX] web{site,_editor}: allow edit en_US field

If the website default language is not en_US, qweb fields are not
translatable in en_US (and thus can't be translated) because:

- the code expected en_US to be the default language.
- there was a error in website _dispatch

opw-746776
closes #17939

addons/web_editor/models/ir_http.py

@@ -11,6 +11,6 @@ class ir_http(orm.AbstractModel):
             request.context['editable'] = True
         if 'edit_translations' in request.httprequest.args and 'edit_translations' not in request.context:
             request.context['edit_translations'] = True
-        if request.context.get('lang') != "en_US" and 'translatable' not in request.context:
+        if request.context.get('edit_translations') and 'translatable' not in request.context:
             request.context['translatable'] = True
         return super(ir_http, self)._dispatch()

addons/website/models/ir_http.py

@@ -160,7 +160,7 @@ class ir_http(orm.AbstractModel):
                     request.uid = None
                     path.pop(1)
                     return self.reroute('/'.join(path) or '/')
-            if path[1] == request.website.default_lang_code:
+            if request.lang == request.website.default_lang_code:
                 request.context['edit_translations'] = False
             if not request.context.get('tz'):
                 request.context['tz'] = request.session.get('geoip', {}).get('time_zone')