Go through db pinning after successful shared secret auth (bug 951946)

https://bugzilla.mozilla.org/show_bug.cgi?id=951946

We weren't pinning properly everytime when using shared secret (when you first go through the db pinning middleware, it's too early, you aren't authenticated yet, so we don't pin you) - oauth was correctly doing this already.

I've done dozens of tests locally, including creating a fake, faulty master/slave configuration and this is the only explanation for bug 951946 that I can find so far, but it's a convincing one. Let's try that on -dev and see what happens.