Before this patch the virtual CPU was the stock qemu CPU, in the sense that
the virtual CPU features were set according to the default qemu CPU.

With this change the CPU features of the host will be copied at start to the
domain definition. This includes features like svm and vmx, which in turn allow
to run nested virtualization if the host is configured accordingly i.e.
`kvm_intel nested=y` in `/etc/modprobe.d/kvm.conf`.

To turn on nesting, a user has to specify `--kvm-cpu-model host-model` when
creating the VM.

Resolves kubernetes#2553

Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>

This patch enables KVM support inside the ISO to support nesting.

Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>

This reverts commit 7a4babe.

For now we just hard-code passthrough.

Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>

With passthrough mode we can enable KVM nesting for guests.

Fixes kubernetes#2553

Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>