add_bgp_peer without bgp_beer_id key is returned with 500 error

It should be returned with 400 error.

Here is error detail.
[root@az2-controller ~]# curl -g -i -X PUT http://192.168.21.120:9696/v2.0/bgp-speakers/7bf585bd-e939-4cfd-a793-4ad3ba901c56/add_bgp_peer -H "Content-Type: application/json" -H "X-Auth-Token: $TOKEN" -d '{}'
HTTP/1.1 500 Internal Server Error
Content-Type: application/json; charset=UTF-8
Content-Length: 150
X-Openstack-Request-Id: req-09ed1bd3-0c0a-4181-945f-5ed0f3513bb6
Date: Thu, 16 Jun 2016 03:18:08 GMT

{"NeutronError": {"message": "Request Failed: internal server error while processing your request.", "type": "HTTPInternalServerError", "detail": ""}}