Add response schema validation for show_default_group_type

This is to add response schema validation for show_default_group_type.

Change-Id: Iaed564689588b1a4fe0a9118e9de330ec0a63e61
partially-implements: blueprint volume-response-schema-validation
diff --git a/tempest/lib/api_schema/response/volume/group_types.py b/tempest/lib/api_schema/response/volume/group_types.py
index bcfa32e..4fc9ae8 100644
--- a/tempest/lib/api_schema/response/volume/group_types.py
+++ b/tempest/lib/api_schema/response/volume/group_types.py
@@ -73,6 +73,18 @@
     }
 }
 
+show_default_group_type = {
+    'status_code': [200],
+    'response_body': {
+        'type': 'object',
+        'properties': {
+            'group_type': common_show_group_type
+        },
+        'additionalProperties': False,
+        'required': ['group_type']
+    }
+}
+
 update_group_type = {
     'status_code': [200],
     'response_body': {
diff --git a/tempest/lib/services/volume/v3/group_types_client.py b/tempest/lib/services/volume/v3/group_types_client.py
index e0bf5e2..1dcd508 100644
--- a/tempest/lib/services/volume/v3/group_types_client.py
+++ b/tempest/lib/services/volume/v3/group_types_client.py
@@ -73,7 +73,7 @@
         url = 'group_types/default'
         resp, body = self.get(url)
         body = json.loads(body)
-        self.expected_success(200, resp.status)
+        self.validate_response(schema.show_default_group_type, resp, body)
         return rest_client.ResponseBody(resp, body)
 
     def show_group_type(self, group_type_id):