[js_auth_client_browser_test] tests improved to run correctly using "grunt test" command

There was a bug: browser tests did not run with 'grunt'. Problem is resolved.
If I understand it right the library is written by us and we can change it right? 

And what is the requirement of using a bind in this case? 
```fetchAuthUrl = helpers.fetchAuthUrl(httpConnection, baseUrl),``` There is no reference to ```this``` inside the helper-node's ```fetchAuthUrl``` function right? All I see is the function making a request and returns the promise and finally based on the response resolves the promise.

If ```baseUrl``` callback function needs a reference then we should then remove the callback function and just pass in the object ( thought that was simpler?? but I am still not sure why we need to bind with an instance)