Add ssh tunneling support to the loadtest about tokenserver

[rfk]

@jbonacci please try out this commit and see if it works for you: 4140d3f

We may need to add some more docs on getting the ssh setup just right, but this seems to work for me.

[jbonacci]

OK. Once I set my .ssh/config file up correctly, this all seems to work.
Long-term solution is here though:
https://github.com/mozilla-services/loads-aws/issues/1

[tarekziade]

ok great to hear it works - I will now shut down all the TCP ports except 22 and 443. And we'll be safe :)