This essentially inverts the x86_64 machines so that '64bit' is
UEFI and instead of a variant 'uefi' machine we have a variant
'bios' machine that is BIOS. The point is to make UEFI testing
the default. We also enable Secure Boot in the UEFI testing,
and add a test of UEFI fallback booting on various products.
Signed-off-by: Adam Williamson <awilliam@redhat.com>
