With Red Hat Enterprise Linux 7, unable to get driverdisk to load automatically like it worked in Red Hat Enterprise Linux 6

Issue

• With Red Hat Enterprise Linux 6, we provided the following option in our isolinux.cfg to add a device driver that was needed to install.

dd=path:/tmp/driverdisk.img

• With Red Hat Enterprise Linux 7 this is not working. I have tried putting the driver disk image in the initrd.img with inst.dd=path:/tmp/driverdisk.img, and also tried putting it directly in the ISO top level directory (like the ks.cfg), and tried referencing with inst.dd=cdrom:/driverdisk.img . That does not work either.