Adds a test for Openvault::SolrHelper that should have been part of prev...

...ious PR. whoops.
actually, i don't think it is, now that I think about it. `Blacklight.solr.commit` will return a hash representing an HTTP response that includes the time it took to run the query. How would it know that, if the call was async? I don't think it could. I'll try removing it and see what happens. Standy by..