Checkmk Werk 10123: Fixed race condition when changing host check command.

ID: 10123 Title: Fixed race condition when changing host check command. Component: cmc Level: 2 Class: Bug fix Version: 1.7.0i1 When the kind of a host check command was changed, e.g. from an active check to smart ping, there was a small time window for scheduling to go wrong. This resulted in endless log lines of the form "invalid command line '@foo' for bar", and the only way to resume normal operation was to restart the Checkmk Micro Core, reloading was not enough. This has been fixed.