virt: Fix virtualization detection

Previously the logic to detect if virt. support was basically available
was broken.
This is now fixed - It can be detected if hardware supporting
virtualization is available and enabled.

rhbz#916823

Change-Id: I0be858555a5ba7af74911925568ac85a0f4edb45
Signed-off-by: Fabian Deutsch <fabiand@fedoraproject.org>