cpuid: eliminate MiniSubtest class

There's no reason to create an additional test object and use confusing
tricks using __new__(), if we already have a test object as the "test"
parameter.

With this, we can convert all test classes to simple functions.

To make sure we kill the VM after running each test case, add
kill_vm=yes and kill_vm_gracefully=no to qemu_cpu.cfg.

Cc: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: NEduardo Habkost <ehabkost@redhat.com>

qemu/tests/cfg/qemu_cpu.cfg

@@ -3,6 +3,8 @@
     virt_test_type = qemu
     type = cpuid
     start_vm = "no"
+    kill_vm = yes
+    kill_vm_gracefully = no
     smp = 1
 
     # ask autotest to not mess with the cpu_model settings