Use whole disk image for Mogan job
Use whole disk image for Mogan job

As we plan to change to only support local boot for partition
images, which needs the image contains grub2, so the default
tempest partition image will break us.

Change-Id: I8dcbdf01af37534e8b6e59482fa29bd573bd981b

openstack-infra/project-config,openstack-infra/project-config