Fix volume v2 capabilities/scheduler-stats tests to test v2 APIs

Currently capabilities/scheduler-stats tests for volume v2 APIs are
making call to v1 API instead of v2. Because api_version is missing in
respective service clients.

This commit fix the issue by specifying the api_version as v2 on
service clients to make API call on v2 endpoints.

Closes-Bug: #1667354

Change-Id: I9002c5ef8b4641597561d2b909bf5914ab8d9995
diff --git a/releasenotes/notes/fix-volume-v2-service-clients-bugfix-1667354-73d2c3c8fedc08bf.yaml b/releasenotes/notes/fix-volume-v2-service-clients-bugfix-1667354-73d2c3c8fedc08bf.yaml
new file mode 100644
index 0000000..6d31576
--- /dev/null
+++ b/releasenotes/notes/fix-volume-v2-service-clients-bugfix-1667354-73d2c3c8fedc08bf.yaml
@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Fix below volume v2 service clients to make v2 API call: Bug#1667354
+
+    - SchedulerStatsClient
+    - CapabilitiesClient
diff --git a/tempest/lib/services/volume/v2/capabilities_client.py b/tempest/lib/services/volume/v2/capabilities_client.py
index b6de5b9..40cb8bf 100644
--- a/tempest/lib/services/volume/v2/capabilities_client.py
+++ b/tempest/lib/services/volume/v2/capabilities_client.py
@@ -19,6 +19,7 @@
 
 
 class CapabilitiesClient(rest_client.RestClient):
+    api_version = "v2"
 
     def show_backend_capabilities(self, host):
         """Shows capabilities for a storage back end.
diff --git a/tempest/lib/services/volume/v2/scheduler_stats_client.py b/tempest/lib/services/volume/v2/scheduler_stats_client.py
index 637254b..3f56f82 100644
--- a/tempest/lib/services/volume/v2/scheduler_stats_client.py
+++ b/tempest/lib/services/volume/v2/scheduler_stats_client.py
@@ -19,6 +19,7 @@
 
 
 class SchedulerStatsClient(rest_client.RestClient):
+    api_version = "v2"
 
     def list_pools(self, detail=False):
         """List all the volumes pools (hosts).