Validate list_instance_usage_audit_log Nova V2 API

This patch adds the JSON schema for list_instance_usage_audit_log Nova
V2 APIs and validate the response of the API with added JSON schema
to block the backward incompatibility change in the future.

Response body of V2 List instance_usage_audit_log is below-

{
    "instance_usage_audit_logs": {
        "hosts_not_run": [
            "%(hostid)s"
        ],
        "log": {},
        "num_hosts": 1,
        "num_hosts_done": 0,
        "num_hosts_not_run": 1,
        "num_hosts_running": 0,
        "overall_status": "0 of 1 hosts done. 0 errors.",
        "period_beginning": "%(timestamp)s",
        "period_ending": "%(timestamp)s",
        "total_errors": 0,
        "total_instances": 0
    }
}

Partially implements blueprint nova-api-attribute-test

Change-Id: I9ecc3afa71b10cfbd3824bb86d02b3232c9a2594
diff --git a/tempest/api_schema/compute/v2/instance_usage_audit_logs.py b/tempest/api_schema/compute/v2/instance_usage_audit_logs.py
index c1509b4..658f574 100644
--- a/tempest/api_schema/compute/v2/instance_usage_audit_logs.py
+++ b/tempest/api_schema/compute/v2/instance_usage_audit_logs.py
@@ -46,3 +46,14 @@
         'required': ['instance_usage_audit_log']
     }
 }
+
+list_instance_usage_audit_log = {
+    'status_code': [200],
+    'response_body': {
+        'type': 'object',
+        'properties': {
+            'instance_usage_audit_logs': common_instance_usage_audit_log
+        },
+        'required': ['instance_usage_audit_logs']
+    }
+}
diff --git a/tempest/services/compute/json/instance_usage_audit_log_client.py b/tempest/services/compute/json/instance_usage_audit_log_client.py
index 4088be9..4700ca7 100644
--- a/tempest/services/compute/json/instance_usage_audit_log_client.py
+++ b/tempest/services/compute/json/instance_usage_audit_log_client.py
@@ -34,6 +34,8 @@
         url = 'os-instance_usage_audit_log'
         resp, body = self.get(url)
         body = json.loads(body)
+        self.validate_response(schema.list_instance_usage_audit_log,
+                               resp, body)
         return resp, body["instance_usage_audit_logs"]
 
     def get_instance_usage_audit_log(self, time_before):