Use Block Storage API v3 instead of API v2

Block Storage API v2 was deprecated during Pike cycle and is being
removed during Xena cycle, and current v3 API should be used instead.

Additional Zuul config for Devstack allows CI to pass which can be
reverted later [1].

[1] https://bugs.launchpad.net/glance/+bug/1938151

Change-Id: Ib66b754f4a0854a0d62d62047a69b04a24434634

Author: kajinamit

.zuul.yaml

@@ -49,6 +49,13 @@
       - magnum_docker_login
     timeout: 2400
 
+- job:
+    name: magnum-tempest-plugin-tests-api-temporary
+    parent: magnum-tempest-plugin-tests-api
+    vars:
+      devstack_localrc:
+        GLANCE_LIMIT_IMAGE_SIZE_TOTAL: 5000
+
 - project:
     templates:
       - openstack-cover-jobs
@@ -58,12 +65,12 @@
       - release-notes-jobs-python3
     check:
       jobs:
-        - magnum-tempest-plugin-tests-api
+        - magnum-tempest-plugin-tests-api-temporary
         - magnum-container-build
     gate:
       queue: magnum
       jobs:
-        - magnum-tempest-plugin-tests-api
+        - magnum-tempest-plugin-tests-api-temporary
     post:
       jobs:
         - magnum-container-publish

magnum/common/clients.py

@@ -13,7 +13,7 @@
 # under the License.
 
 from barbicanclient.v1 import client as barbicanclient
-from cinderclient.v2 import client as cinder_client
+from cinderclient.v3 import client as cinder_client
 from glanceclient import client as glanceclient
 from heatclient import client as heatclient
 from keystoneauth1.exceptions import catalog