Checkmk Werk 11257: Docker contianer: Fix container detection in podman containers

ID: 11257 Title: Docker contianer: Fix container detection in podman containers Component: Core & setup Level: 1 Class: Bug fix Version: 1.7.0i1 Checkmk needs to detect the execution in the container to be able to handle the site creation correctly. This failed in podman containers, because they use the "/.containerenv" file in the root filesystem instead of the "/.dockerenv".