Don't error out on template items of unknown kind

Fixes:
```
[bparees@bparees ~/git/gocode/src/github.com/openshift/origin/examples/simple-ruby-app]$ openshift kube process -c template/template.json > processed/template.processed.json
F0919 17:31:50.027251 29007 kubecfg.go:456] failed to process template: request [&http.Request{Method:"POST", URL:(*url.URL)(0xc21006e4d0), Proto:"HTTP/1.1", ProtoMajor:1, ProtoMinor:1, Header:http.Header{}, Body:ioutil.nopCloser{Reader:(*bytes.Buffer)(0xc21006e3f0)}, ContentLength:2548, TransferEncoding:[]string(nil), Close:false, Host:"localhost:8080", Form:url.Values(nil), PostForm:url.Values(nil), MultipartForm:(*multipart.Form)(nil), Trailer:http.Header(nil), RemoteAddr:"", RequestURI:"", TLS:(*tls.ConnectionState)(nil)}] failed (500) 500 Internal Server Error: {"kind":"Status","creationTimestamp":null,"apiVersion":"v1beta1","status":"failure","message":"Invalid template config: errors.ErrorList{errors.ValidationError{Type:\"fieldValueInvalid\", Field:\"items[1].kind\", BadValue:\"runtime.Object\"}}","code":500}
```