Allows libvirt to set a serial number for a volume

The serial number defaults to the volume_id of the volume being
attached. We may expose a method in the future to set a different
serial number when creating or attaching a volume.

The purpose of this change is to give users a consistent place
they can find their volume. It should show up now in most flavors
of linux under /disk/by-id/virtio-<volume_uuid>

Fixes bug 1004328

Change-Id: Id1c56b5b23d799deb7da2d39ae57ecb48965c55f

nova/tests/test_libvirt.py

@@ -154,6 +154,24 @@ class LibvirtVolumeTestCase(test.TestCase):
             'host': 'fake_host'
         }
 
+    def test_libvirt_volume_driver_serial(self):
+        vol_driver = volume_driver.VolumeDriver()
+        libvirt_driver = volume.LibvirtVolumeDriver(self.fake_conn)
+        name = 'volume-00000001'
+        vol = {'id': 1, 'name': name}
+        connection_info = {
+            'driver_volume_type': 'fake',
+            'data': {
+                    'device_path': '/foo',
+                },
+            'serial': 'fake_serial',
+        }
+        mount_device = "vde"
+        conf = libvirt_driver.connect_volume(connection_info, mount_device)
+        tree = conf.format_dom()
+        self.assertEqual(tree.get('type'), 'block')
+        self.assertEqual(tree.find('./serial').text, 'fake_serial')
+
     def test_libvirt_iscsi_driver(self):
         # NOTE(vish) exists is to make driver assume connecting worked
         self.stubs.Set(os.path, 'exists', lambda x: True)