Fix problem causing to add number of events in Boole output

A problem was found in production during tests to produce 'MDF' files. The tests were carried out setting the number of events for 'Boole' to process and that caused to add it to the filename changing it from what expect by 'LHCbDirac'.

Details can be found in LHCBGAUSS-1435 comments.

Tests showed that the only files or combination for which this worked correctly was 'XDIGI' and 'XDIGI'+'MDF'.

By change the standard production with 'DIGI' are not affected because 'Boole' is executed in a separate transformation with the number of events to process set to '-1' for which the 'Boole' configurable does not add the number of events to the filename.

I have fixes the 'MDF' and added the 'DIGI'. In case a 'XDIGI' is also present it overwrites a 'DIGI' it would be in the list, since a 'DIGI' should not be written if an 'XDIGI' since it is its subset.

cc: @cattanem