This is a similar image than the hardened one, but it has some
differences:
- removes the blacklist of vfat module, as we need it
- Sets DIB_BLOCK_DEVICE to efi instead of mbr
- Uses the overcloud-secure-uefi element, that creates the proper layout
Change-Id: I0e1c79462da170fb9dc99e12c05817b9f565c0de
Depends-On: If9e0504438632f1a22b45b7c95e7bfb8cb6f41d3
21b575a575