virt.kvm_vm: Set driver_type attribute for kvm_vm

This way we fix a bug introduced by f552a00, where we
start checking out driver_type to verify if some xen
installation hacks were needed during unattended install
setup.

Signed-off-by: Lucas Meneghel Rodrigues <lmr@redhat.com>

client/virt/kvm_vm.py

@@ -74,6 +74,7 @@ def __init__(self, name, params, root_dir, address_cache, state=None):
         # }
         # This structure can used in usb hotplug/unplug test.
         self.usb_dev_dict = {}
+        self.driver_type = 'kvm'
 
 
     def verify_alive(self):