Check_MK Werk 6505: Avoid CMC crash during event helper restarts.

ID: 6505 Title: Avoid CMC crash during event helper restarts. Component: Core & setup Level: 1 Class: Bug fix Version: 1.6.0i1 When an event helper (for notifications/alerts) should be restarted, the Check_MK Micro Core could go into an infinite recursion, ultimately leading to a crash of the CMC itself. This has been fixed. CMK-1117