Change network/interfaces clients to return one value and update tests

Partially implements: blueprint clients-return-one-value

Change-Id: I79802333e984e04618c71a0e8fa4923109a93374
diff --git a/tempest/services/compute/json/interfaces_client.py b/tempest/services/compute/json/interfaces_client.py
index 595b23c..0c5516c 100644
--- a/tempest/services/compute/json/interfaces_client.py
+++ b/tempest/services/compute/json/interfaces_client.py
@@ -29,7 +29,8 @@
         resp, body = self.get('servers/%s/os-interface' % server)
         body = json.loads(body)
         self.validate_response(schema.list_interfaces, resp, body)
-        return resp, body['interfaceAttachments']
+        return service_client.ResponseBodyList(resp,
+                                               body['interfaceAttachments'])
 
     def create_interface(self, server, port_id=None, network_id=None,
                          fixed_ip=None):
@@ -45,28 +46,28 @@
         resp, body = self.post('servers/%s/os-interface' % server,
                                body=post_body)
         body = json.loads(body)
-        return resp, body['interfaceAttachment']
+        return service_client.ResponseBody(resp, body['interfaceAttachment'])
 
     def show_interface(self, server, port_id):
         resp, body = self.get('servers/%s/os-interface/%s' % (server, port_id))
         body = json.loads(body)
-        return resp, body['interfaceAttachment']
+        return service_client.ResponseBody(resp, body['interfaceAttachment'])
 
     def delete_interface(self, server, port_id):
         resp, body = self.delete('servers/%s/os-interface/%s' % (server,
                                                                  port_id))
         self.validate_response(common_schema.delete_interface, resp, body)
-        return resp, body
+        return service_client.ResponseBody(resp, body)
 
     def wait_for_interface_status(self, server, port_id, status):
         """Waits for a interface to reach a given status."""
-        resp, body = self.show_interface(server, port_id)
+        body = self.show_interface(server, port_id)
         interface_status = body['port_state']
         start = int(time.time())
 
         while(interface_status != status):
             time.sleep(self.build_interval)
-            resp, body = self.show_interface(server, port_id)
+            body = self.show_interface(server, port_id)
             interface_status = body['port_state']
 
             timed_out = int(time.time()) - start >= self.build_timeout
@@ -78,7 +79,7 @@
                             self.build_timeout))
                 raise exceptions.TimeoutException(message)
 
-        return resp, body
+        return body
 
     def add_fixed_ip(self, server_id, network_id):
         """Add a fixed IP to input server instance."""
@@ -91,7 +92,7 @@
                                post_body)
         self.validate_response(servers_schema.server_actions_common_schema,
                                resp, body)
-        return resp, body
+        return service_client.ResponseBody(resp, body)
 
     def remove_fixed_ip(self, server_id, ip_address):
         """Remove input fixed IP from input server instance."""
@@ -104,4 +105,4 @@
                                post_body)
         self.validate_response(servers_schema.server_actions_common_schema,
                                resp, body)
-        return resp, body
+        return service_client.ResponseBody(resp, body)