Belgian point-of-sale systems can now fall back to a websocket connection when the usual longpolling connection to the blackbox is unavailable. This temporary improvement helps keep fiscal device communication more reliable until the newer IoT HTTP service replaces it in a later version.

We updated the way of contacting the blackbox to allow using the websocket as a 
fallback for the longpolling.
This is a temporary fix that is solved by the use of the `iot_http` service in 
saas-18.4.

Community PR: odoo/odoo#212052
Task: 4824066