The keystone jobs test Redfish+Legacy+PXE, add one more job
with Redfish+UEFI (and intention to switch it to virtual media).
Only Fedora works reliably now. CentOS ships with an OVMF firmware
that seems to require secure boot, Ubuntu has problems with TFTP.
Make testing VM configuration much closer to what works in devstack.
Change-Id: Ic231e16f34176187d6179219356fd3c1de885423