Checkmk Werk 13231: Fix source of painter "Docker node"

ID: 13231 Title: Fix source of painter "Docker node" Component: Multisite Level: 1 Class: Bug fix Version: 2.1.0i1 The painter, used in views like e.g. "Docker containers", used host labels as its source. That could lead to wrong results, if the container is already running on another node but the host label was not updated yet. We now take the service "Docker container status" to determine the current node of a container.