Checkmk Werk 12085: Use Python2 pendant of mailman_lists agent plugin

ID: 12085 Title: Use Python2 pendant of mailman_lists agent plugin Component: Checks & agents Level: 1 Class: Bug fix Version: 2.1.0i1 Porting the {{mailman_lists}} agent plugin does not work out of the box due to the way the executable is used as a plugin. Prior to a real porting this change just rolls back to Python2 for this plugin.