Add cinder multi-backend tests

This commit updates templates/openstack_tempest_gate.sh.j2 and the
default tempest_test_whitelist to expose a cinder multi-backend test.
This is useful for ensuring that a) multiple backends are operational
(ceph/LVM for instance), while also testing that the multi-backend
features are functional.

NOTE: We also change the tests to use the sahara tempest plugin rather
      than designate as the designate plugin appears to be broken at
      the moment.

Change-Id: I4a730614cfb695b82a79dfbe540396e5f4fd198a

defaults/main.yml

@@ -63,6 +63,7 @@ tempest_test_whitelist:
   - "{{ (tempest_service_available_nova | bool) | ternary('tempest.scenario.test_server_basic_ops', '') }}"
   - "{{ (tempest_service_available_swift | bool) | ternary('tempest.scenario.test_object_storage_basic_ops', '') }}"
   - "{{ (tempest_volume_backup_enabled | bool) | ternary('tempest.api.volume.admin.test_volumes_backup', '') }}"
+  - "{{ (tempest_volume_multi_backend_enabled | bool) | ternary('tempest.api.volume.admin.test_multi_backend', '') }}"
 
 # Toggle fatal deprecations
 tempest_fatal_deprecations: False

templates/openstack_tempest_gate.sh.j2

@@ -67,6 +67,11 @@ function gen_test_list_cinder_backup {
   egrep 'tempest\.api\.volume\.admin\.test_volumes_backup'
 }
 
+# Run the cinder multi-backend tests
+function gen_test_list_cinder_multi_backend {
+  egrep 'tempest\.api\.volume\.admin\.test_multi_backend'
+}
+
 # Run ceilometer api tests
 function gen_test_list_ceilometer_api {
   egrep 'tempest\.api\.telemetry'

tests/os_tempest-overrides.yml

@@ -18,8 +18,8 @@ tempest_run: yes
 
 # A sample plugin to activate the code path
 tempest_plugins:
-  - name: designate-tempest-plugin
-    repo: https://git.openstack.org/openstack/designate-tempest-plugin
+  - name: sahara-tests
+    repo: https://git.openstack.org/openstack/sahara-tests
     branch: master
 
 neutron_provider_networks: