Comment 82 for bug 1787405

Seems to me like:
4.7 d6f97d13 "qemu: mdev: Use vfio-pci 'display' property only with vfio-pci mdevs"

Related:
4.6 d48813e8 conf: Introduce new video type 'none'
4.6 c0ca6dcf qemu: command: Enable formatting vfio-pci.display option onto cmdline
4.6 d54e45b6 conf: Introduce new <hostdev> attribute 'display'
4.6 11c7bdac qemu: caps: Add vfio-pci.display capability

I think the appearance of the 4.6 changes I referred made the 4.7 change above needed.
Lets spin a PPA with just this on top and retest this.

If good we can push it to disco and on top the cosmic SRU (and release it as one update).