Verify list agents attributes of V2/V3 APIs

This patch adds the JSON schema for Nova V2/V3 list agents APIs
includes the attributes to block the backward incompatibility change
in the future.

The response body of v2 and v3 API is the below:

{
    "agents": [
        {
            "agent_id": 1,
            "hypervisor": "xen",
            "os": "linux",
            "architecture": "x86",
            "version": "7.0",
            "url": "xxx://xxx/xxx/xxx1",
            "md5hash": "add6bb58e139be103324d04d82d8f546"
        }
    ]
}

Partially implements blueprint nova-api-attribute-test

Change-Id: I59fc1a54b32554d7c9827ce912d3197f78c4cd12
diff --git a/tempest/api_schema/compute/agents.py b/tempest/api_schema/compute/agents.py
new file mode 100644
index 0000000..b04cf64
--- /dev/null
+++ b/tempest/api_schema/compute/agents.py
@@ -0,0 +1,40 @@
+# Copyright 2014 NEC Corporation.  All rights reserved.
+#
+#    Licensed under the Apache License, Version 2.0 (the "License"); you may
+#    not use this file except in compliance with the License. You may obtain
+#    a copy of the License at
+#
+#         http://www.apache.org/licenses/LICENSE-2.0
+#
+#    Unless required by applicable law or agreed to in writing, software
+#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+#    License for the specific language governing permissions and limitations
+#    under the License.
+
+list_agents = {
+    'status_code': [200],
+    'response_body': {
+        'type': 'object',
+        'properties': {
+            'agents': {
+                'type': 'array',
+                'items': {
+                    'type': 'object',
+                    'properties': {
+                        'agent_id': {'type': ['integer', 'string']},
+                        'hypervisor': {'type': 'string'},
+                        'os': {'type': 'string'},
+                        'architecture': {'type': 'string'},
+                        'version': {'type': 'string'},
+                        'url': {'type': 'string', 'format': 'uri'},
+                        'md5hash': {'type': 'string'}
+                    },
+                    'required': ['agent_id', 'hypervisor', 'os',
+                                 'architecture', 'version', 'url', 'md5hash']
+                }
+            }
+        },
+        'required': ['agents']
+    }
+}
diff --git a/tempest/services/compute/json/agents_client.py b/tempest/services/compute/json/agents_client.py
index 19821e7..98d8896 100644
--- a/tempest/services/compute/json/agents_client.py
+++ b/tempest/services/compute/json/agents_client.py
@@ -15,6 +15,7 @@
 import json
 import urllib
 
+from tempest.api_schema.compute import agents as common_schema
 from tempest.api_schema.compute.v2 import agents as schema
 from tempest.common import rest_client
 from tempest import config
@@ -37,7 +38,9 @@
         if params:
             url += '?%s' % urllib.urlencode(params)
         resp, body = self.get(url)
-        return resp, json.loads(body).get('agents')
+        body = json.loads(body)
+        self.validate_response(common_schema.list_agents, resp, body)
+        return resp, body['agents']
 
     def create_agent(self, **kwargs):
         """Create an agent build."""
diff --git a/tempest/services/compute/v3/json/agents_client.py b/tempest/services/compute/v3/json/agents_client.py
index e1c286c..48be54c 100644
--- a/tempest/services/compute/v3/json/agents_client.py
+++ b/tempest/services/compute/v3/json/agents_client.py
@@ -15,6 +15,7 @@
 import json
 import urllib
 
+from tempest.api_schema.compute import agents as common_schema
 from tempest.api_schema.compute.v3 import agents as schema
 from tempest.common import rest_client
 from tempest import config
@@ -34,7 +35,9 @@
         if params:
             url += '?%s' % urllib.urlencode(params)
         resp, body = self.get(url)
-        return resp, self._parse_resp(body)
+        body = json.loads(body)
+        self.validate_response(common_schema.list_agents, resp, body)
+        return resp, body['agents']
 
     def create_agent(self, **kwargs):
         """Create an agent build."""