Instance cloud-init cannot reach neutron-metadata-agent due to a 404 error message in Red Hat OpenStack Platform

Issue

neutron-metadata-agent in the log files shows the error

Unauthorized: {"error": {"message": "The resource could not be found.", "code": 404, "title": "Not Found"}}

When this happens, new provisioning of instances is impacted because instances' Cloudinit cannot contact the metadata agent. A restart of neutron-metadata-agent fixes the issue temporarily.