Make trivial diagnosticType default

When no diagnosticType or other relevant query parameters are provided to the `grouper_root/status` request, it would be nice if it was handled as if a 'trivial' diagnosticType had been requested instead of raising an error.

I sometimes want to check status when I've just brought Grouper up. I usually either forget that there is a required query parameter or cannot remember exactly what it is, so then I have to fix the URL and send the request again.

It's a small annoyance, but sometimes small ones have an outsize effect.