The resulting signed VMware OVA fails to load in vCenter. During validation of the OVF file in vCenter, a failure message results:

Issues detected with selected template. Details: - 68:7:VALUE_ILLEGAL: Value ''5'' of Parent element does not refer to a ref of type DiskControllerReference.

The cdrom0 is being attached to the serial0 interface. Changing the parent from 5 to 4 fixes the problem by setting the cdrom0 parent to the IDE controller in the scripts/template.ovf file.