[MM-51329] server/config: add validation for local mode socket file (#23180)

server/i18n/en.json

@@ -8811,6 +8811,10 @@
     "id": "model.config.is_valid.listen_address.app_error",
     "translation": "Invalid listen address for service settings Must be set."
   },
+  {
+    "id": "model.config.is_valid.local_mode_socket.app_error",
+    "translation": "Unable to locate local socket file directory."
+  },
   {
     "id": "model.config.is_valid.localization.available_locales.app_error",
     "translation": "Available Languages must contain Default Client Language."