Remove outer module block from unit tests

So that our tests aren't extending and implicitly namespaced into the
`Vcloud` module. This will make it more obvious where we're crossing the
boundaries of different projects. It will also instantiate the class given
(without any args) and make it available as `subject` which may allow us to
DRY up some of our tests.
Use subject in Launcher::Launch unit tests

The outer describe block sets this up for us. Since we don't need to pass
any arguments to the class itself (only the methods) and the methods are
public (unlike VappOrchestrator).