CWL: avoid duplicate file names with no calling batches
CWL: avoid duplicate file names with no calling batches

When grouping together pre-called variant inputs for validation, avoid using
batch names as outputs since these are not called together (only evaluated
together) and don't contain all sample inputs.

chapmanb/bcbio-nextgen,a113n/bcbio-nextgen,lbeltrame/bcbio-nextgen,vladsaveliev/bcbio-nextgen,lbeltrame/bcbio-nextgen,chapmanb/bcbio-nextgen,chapmanb/bcbio-nextgen,vladsaveliev/bcbio-nextgen,a113n/bcbio-nextgen,a113n/bcbio-nextgen,vladsaveliev/bcbio-nextgen,lbeltrame/bcbio-nextgen