Ensure single unsorted BAM files get merged
Ensure single unsorted BAM files get merged

Handles align_split_size cases where the size is bigger than available
reads and we only create one partition. Correctly does the post
align sort and merge. Thanks to @guillermo-carrasco

biocyberman/bcbio-nextgen,Cyberbio-Lab/bcbio-nextgen,gifford-lab/bcbio-nextgen,mjafin/bcbio-nextgen,mjafin/bcbio-nextgen,chapmanb/bcbio-nextgen,chapmanb/bcbio-nextgen,biocyberman/bcbio-nextgen,vladsaveliev/bcbio-nextgen,mjafin/bcbio-nextgen,lbeltrame/bcbio-nextgen,vladsaveliev/bcbio-nextgen,vladsaveliev/bcbio-nextgen,brainstorm/bcbio-nextgen,lbeltrame/bcbio-nextgen,Cyberbio-Lab/bcbio-nextgen,chapmanb/bcbio-nextgen,lbeltrame/bcbio-nextgen,a113n/bcbio-nextgen,brainstorm/bcbio-nextgen,a113n/bcbio-nextgen,Cyberbio-Lab/bcbio-nextgen,brainstorm/bcbio-nextgen,biocyberman/bcbio-nextgen,a113n/bcbio-nextgen,gifford-lab/bcbio-nextgen,gifford-lab/bcbio-nextgen