fix job splitting for ACDC MCFakeFile

This commit should fix two things (do NOT merge yet):
 a) when creating production jobs out of ACDC documents ( for MCFakeFile), do not use the fileset/lfn number of events (it corresponds to 250 jobs actually). Instead, create a job to recover only those missing lumis.
 b) take into account changes applied to the job splitting (EventBased) set for the new ACDC workflow -> TO BE FIXED
This still creates one job if the file contains smaller events than eventsPerJob.
i.e, if eventsPerJob = 1000, and file contains 100 events, it will still create one job in stead of taking multiple files to create one job. Is it desirable? I see original (not ACDC) algorithm doing the same thing.
https://github.com/dmwm/WMCore/blob/master/src/python/WMCore/JobSplitting/EventBased.py#L114

So I wonder whether that is the restriction to follow or something need to be fixed (take multiple files to create a job if files contains small amount of events)