Checkmk Werk 13272: prometheus_build: show Prometheus version optionally

ID: 13272 Title: prometheus_build: show Prometheus version optionally Component: Checks & agents Level: 1 Class: Bug fix Version: 2.1.0i1 In the previous version, the prometheus_build check always expected a version associated with the connecting Prometheus API. This effectively led to an error when the version was not included. This werk fixes this behaviour.