Extend test case in order to explain return.

If the `return` is present this test case will end with:
```
Error: Error on retrieving access_token after 10 attempts.
Error: Error: DEPTH_ZERO_SELF_SIGNED_CERT
```

If the `return` is NOT present the code execution fails with:
```
TypeError: Cannot read property 'statusCode' of undefined
    at Request._callback (/Users/heichler/dev/3rd/sphere-node-connect/lib/rest.js:101:21)
```

You can simply test this by changing the default host name in line 15 of auth2.coffee to some stupid value.