backup_restore.js fails when observing FTDC interim files

The backup_restore.js tests blacklists certain lock files that should not be copied when doing a backup. That blacklist was not updated to deal with ephemeral files generated by the FTDC subsystem.

Either FTDC needs to change its approach to ephemeral files, or the blacklist upon which backup_restore makes its decision needs to be updated. If the latter approach is taken, our documentation for how to perform a live system backup must be updated.