Set up a Torperf to a hidden service

It would be great to get an ongoing torperf run that's accessing a hidden service, so we can track performance of those over time also.

The simple part here is setting up a hidden service that's probably not the performance bottleneck, and setting up a torperf install as usual.

The complex part here is that the Tor client will cache the hidden service descriptor, and maybe even the rendezvous circuit (in the case of the every-five-minute 50kb fetch), skewing our results.