@agorrod, @michaelcahill: the fixes to allow hot-backups to run concurrently with bulk-loading files.
Ref WT-653, WT-570.
WT-566 Backup returns EBUSY when used in conjunction with LSM
WT-653 Hot backup of files that are being bulk loaded
WT-570 Add a test that attempts a backup while a bulk load is happening.