Check_MK Werk 2894: Fixed broken cluster checks when using Nagios core

ID: 2894 Title: Fixed broken cluster checks when using Nagios core Component: Core & Setup Level: 2 Class: Bug Fix Version: 1.2.7i4 When monitoring clustered hosts using Nagios as core, the Check_MK service always resulted in an UNKNOWN state and this exception: NameError: global name 'set_use_cachefile' is not defined