Checkmk Werk 11997: mk_docker.py: Handle parallel calls of the plugin

ID: 11997 Title: mk_docker.py: Handle parallel calls of the plugin Component: Checks & agents Level: 1 Class: Bug fix Version: 2.1.0i1 The docker API will not allow parallel calls to its 'df' command. Since this command is notoriously long running, the section 'docker_node_disk_usage' was often missing if the agent has been called multiple times in parallel.