Added discovery api loader.

@nexus-uw could you please review. Thanks!
@rodrigopavezi this should be 
```
discoveryAPILoader().then(function () {
...
})
.then(null,done);
```
so as to catch the any errors in the resolved handler. ie if discovery was no loaded.Currently if the test fails inside the resolved function, the test will just timeout (which is not helpful for finding out why)