Avoid use of qt param for the DIH in the admin UI

I really, really dislike that the qt parameter can used to refer to request handlers starting with a '/', especially for non-search handlers. The admin UI has one place I am aware of that attempts to do this, which is the DIH's admin page. Since we have two UIs in trunk, the new and old, there are actually two UIs where this occurs, and the old UI has two related files that need updating, in order to address this issue.

An example URL generated by the UI today is this:
http://localhost:8983/solr/rss/select?qt=/dataimport&command=show-config
And here it is without using qt:
http://localhost:8983/solr/rss/dataimport?command=show-config

I do realize that fixing this issue as I do in my patch will make the UI not work if the DIH isn't registered with a leading '/', but honestly I wonder who if anyone out there does that. And even then, it's easily rectified.