Invalid keyname translated to null on create server

Invalid keyname translated to null on create server
400 bad request should raise for the case a user mistype keyname.

Test:
curl -i -H "x-auth-token: $AUTHTOKEN" -H "content-type: application/json" -d '{"server":{"name":"fuga","imageRef":2,"flavorRef":3,"KeyPair":"fuga"}}' $APIURL/v1.1/2/servers
HTTP/1.1 202 Accepted
Content-Type: application/json
Content-Length: 718
Date: Wed, 16 Nov 2011 23:49:50 GMT

{"server": {"status": "BUILD", "updated": "2011-11-16T23:49:50Z", "hostId": "", "user_id": "demo", "name": "fuga", "links": [{"href": "http://127.00.1:8774/v1.1/2/servers/6", "rel": "self"}, {"href": "http://127.00.1:8774/2/servers/6", "rel": "bookmark"}], "addresses": {}, "tenant_id": "2", "image": {"id": "2", "links": [{"href": "http://127.00.1:8774/2/images/2", "rel": "bookmark"}]}, "created": "2011-11-16T23:49:50Z", "uuid": "2be30959-3f4c-4477-bc0c-6050855b1233", "accessIPv4": "", "accessIPv6": "", "key_name": null, "adminPass": "FxPyk3MLhSqxbW4T", "progress": 0, "flavor": {"id": "3", "links": [{"href": "http://127.00.1:8774/2/flavors/3", "rel": "bookmark"}]}, "config_drive": "", "id": 6, "metadata": {}}}