Die on `kitchen login` if instance is not created.

This is solved slightly differently in than in #462 because otherwise the Instance cannot be checked for a "non-implemented" exception (not all drivers necessarily support the login command).

Closes #375
Closes #462

Thanks to @@daniellockard, @juliandunn, and @dje!

![hackers1](https://cloud.githubusercontent.com/assets/261548/4686580/801cf8aa-5647-11e4-94e6-da07f2bc3a27.gif)