Bug 1045966 — Add a tool that let us validate the Service Provider.

https://bugzilla.mozilla.org/show_bug.cgi?id=1045966
If we do it directly in the code, it will probably work only for loop.
If we provide the curl command, the assertion will be valid for different Service Provider and we will be able to modify it to validate any of them (Marketplace, Firefox Hello, Firefox Messaging etc.)