Transaction: avoid race conditions
Transaction: avoid race conditions

Transactional size checks can fail when multiple processes are
creating and validing the same file and it gets moved in one process
while the other still needs to check. This skips the final check in
those cases to avoid failing out entirely. Thanks to @ssaif

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