virt-test: fix disable-kvm once more

If config has only 'disable-kvm=yes' but not 'enable-kvm=no'
qemu will be started in kvm mode and with kvm disabled at
compile time it fails to launch.

Currently disable/enable-kvm config options and qemu supported
options are intermingled in a bunch of ifs, separate apples
and oranges in different bins and make logic straightforward:

* alias disable-kvm to enable-kvm param
* get right option set to disable/enable kvm on qemu/qemu-kvm
* set appropriate option depending on value of param enable-kvm
Signed-off-by: NIgor Mammedov <imammedo@redhat.com>

qemu/tests/cfg/qemu_cpu.cfg

@@ -30,7 +30,6 @@
                     # if 'vendor' is missing then host's vendor value is used
                     # kvm by default overides vendor with host's value
                 - nokvm:
-                    enable_kvm = "no"
                     disable_kvm = "yes"
                     variants:
                         - intel: