Apparently, now days system boot chain is tempted to display
fancy things on the console. While enjoyable, in non-text mode
libvirt guest console can't make it to the log file.
This change tries to ensure pure text mode kernel console in
PXE and Redfish booting by disabling any graphics in the VM
and in guest kernel.
Note that it's not only kernel that can control display mode,
but EFI boot loader as well.
For getting on VM's text console in devstack one could use
`virsh console --devname serial1 node-0` or just add `<graphics>`
section to `virsh edit node-0` XML.