Bug 1079950 — Add a test to make sure GET /calls returns the callerId if present.

https://bugzilla.mozilla.org/show_bug.cgi?id=1079950
You cannot just call an endpoint, you need to create a scenario to make a direct call setup.
Here we are just making sure POST /fxa-params/token save the userId which is the bug we are solving.

We should be able to merge both tests here if you want to but as you asked for unit test before I split them.