Checkmk Werk 12373: agent_prometheus: fixing piggyback host names

ID: 12373 Title: agent_prometheus: fixing piggyback host names Component: Checks & agents Level: 1 Class: Bug fix Version: 2.1.0i1 In the previous version, some piggyback hosts generated by the Prometheus special agent were prepended by underscores. This werk fixes the name formatting to remove these characters.