Make rbd.libvirt_info parent class compatible

commit 7a34be0ec0cd0cb9555fe64ff6c486faae1ae91d from
https://github.com/openstack/nova

Rbd.libvirt_info function definition misses hypervisor_version argument added in change:
https://review.openstack.org/32379

Closes-Bug: #1233188
Change-Id: Ib68d743e783af0f6d82d2ba180869ee642e86050

diff --git a/nova/tests/virt/libvirt/test_imagebackend.py b/nova/tests/virt/libvirt/test_imagebackend.py
index 2455ec8..5bfa94d 100644
--- a/nova/tests/virt/libvirt/test_imagebackend.py
+++ b/nova/tests/virt/libvirt/test_imagebackend.py
@@ -20,6 +20,8 @@ import os
 import fixtures
 from oslo.config import cfg
 
+from inspect import getargspec
+
 from nova import exception
 from nova.openstack.common import uuidutils
 from nova import test
@@ -630,6 +632,10 @@ class RbdTestCase(_ImageTestCase, test.NoDBTestCase):
 
         self.assertEqual(fake_processutils.fake_execute_get_log(), [])
 
+    def test_parent_compatible(self):
+        self.assertEqual(getargspec(imagebackend.Image.libvirt_info),
+             getargspec(self.image_class.libvirt_info))
+
 
 class BackendTestCase(test.NoDBTestCase):
     INSTANCE = {'name': 'fake-instance',
diff --git a/nova/virt/libvirt/imagebackend.py b/nova/virt/libvirt/imagebackend.py
index e900789..51872cf 100644
--- a/nova/virt/libvirt/imagebackend.py
+++ b/nova/virt/libvirt/imagebackend.py
@@ -482,7 +482,7 @@ class Rbd(Image):
         return hosts, ports
 
     def libvirt_info(self, disk_bus, disk_dev, device_type, cache_mode,
-            extra_specs):
+            extra_specs, hypervisor_version):
         """Get `LibvirtConfigGuestDisk` filled for this image.
 
         :disk_dev: Disk bus device name