Fixes for file-based filter farm

This request removes the hostname from the INIT message header. The header encoded the hostname where the INIT message is created. This was useful for the old StorageManager in DAQ1. However, for the FFF, this information is misleading as only one INIT file is preserved which contains a random hostname. In addition, it causes problems to easily check that the INIT messages are identical (beside the hostname). The hostname is also found in each event header. Therefore, it is still possible to trace back any event to its origin in case of data corruption.

In addition, there are a couple of fixes for the file-based filter farm.