Wrap volume_backup's update function with api_version

Volume backup's update function only supports 3.9 microversion
or higher. So it should be wrapped like like this one[1],
otherwise these fuctions may be exposed to lib users with old
microversion.

[1]: https://github.com/openstack/python-cinderclient/blob/master/cinderclient/v3/services.py#L82

Change-Id: I2c800099e8ae707135417f9821f14d1a9e69586e

cinderclient/tests/unit/v3/test_volume_backups.py

@@ -13,19 +13,25 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-
 from cinderclient.tests.unit import utils
 from cinderclient.tests.unit.v3 import fakes
-
-cs = fakes.FakeClient()
+from cinderclient import api_versions
+from cinderclient import exceptions as exc
 
 
 class VolumesTest(utils.TestCase):
 
     def test_update(self):
+        cs = fakes.FakeClient(api_version=api_versions.APIVersion('3.9'))
         b = cs.backups.get('1234')
         backup = b.update(name='new-name')
         cs.assert_called(
             'PUT', '/backups/1234',
             {'backup': {'name': 'new-name'}})
         self._assert_request_id(backup)
+
+    def test_pre_version(self):
+        cs = fakes.FakeClient(api_version=api_versions.APIVersion('3.8'))
+        b = cs.backups.get('1234')
+        self.assertRaises(exc.VersionNotFoundForAPIMethod,
+                          b.update, name='new-name')

cinderclient/v3/volume_backups.py

@@ -16,6 +16,7 @@
 """
 Volume Backups interface (v3 extension).
 """
+from cinderclient import api_versions
 from cinderclient import base
 from cinderclient.openstack.common.apiclient import base as common_base
 
@@ -131,6 +132,7 @@ class VolumeBackupManager(base.ManagerWithFind):
         resp, body = self.api.client.post("/backups/import_record", body=body)
         return common_base.DictWithMeta(body['backup'], resp)
 
+    @api_versions.wraps("3.9")
     def update(self, backup, **kwargs):
         """Update the name or description for a backup.