Fix chimeric alignments with STAR.
Fix chimeric alignments with STAR.

Thanks to Ivan De Dios and Suraj Menon for bringing up the issue.

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