Validate get fixed-ips attributes of Nova V2 API

This patch adds the JSON schema for Nova V2 get fixed-ips API
response and validate the response with added JSON schema to
block the backward incompatibility change in the future.

The response body of V2 get fixed-ip API is below:

{
    "fixed_ip": {
        "address": "192.168.1.1",
        "cidr": "192.168.1.0/24",
        "host": "host",
        "hostname": "openstack"
    }
}

Partially implements blueprint nova-api-attribute-test

Change-Id: I1b8b2c00492e85e6075c036b41f28e68357da653
diff --git a/tempest/api_schema/compute/v2/fixed_ips.py b/tempest/api_schema/compute/v2/fixed_ips.py
new file mode 100644
index 0000000..a6add04
--- /dev/null
+++ b/tempest/api_schema/compute/v2/fixed_ips.py
@@ -0,0 +1,36 @@
+# 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.
+
+fixed_ips = {
+    'status_code': [200],
+    'response_body': {
+        'type': 'object',
+        'properties': {
+            'fixed_ip': {
+                'type': 'object',
+                'properties': {
+                    'address': {
+                        'type': 'string',
+                        'format': 'ip-address'
+                    },
+                    'cidr': {'type': 'string'},
+                    'host': {'type': 'string'},
+                    'hostname': {'type': 'string'}
+                },
+                'required': ['address', 'cidr', 'host', 'hostname']
+            }
+        },
+        'required': ['fixed_ip']
+    }
+}
diff --git a/tempest/services/compute/json/fixed_ips_client.py b/tempest/services/compute/json/fixed_ips_client.py
index 8b2c6c9..5fdd564 100644
--- a/tempest/services/compute/json/fixed_ips_client.py
+++ b/tempest/services/compute/json/fixed_ips_client.py
@@ -15,6 +15,7 @@
 
 import json
 
+from tempest.api_schema.compute.v2 import fixed_ips as schema
 from tempest.common import rest_client
 from tempest import config
 
@@ -31,6 +32,7 @@
         url = "os-fixed-ips/%s" % (fixed_ip)
         resp, body = self.get(url)
         body = json.loads(body)
+        self.validate_response(schema.fixed_ips, resp, body)
         return resp, body['fixed_ip']
 
     def reserve_fixed_ip(self, ip, body):