CC should raise error when no DEA available to run a APP instance.

Now `cf push` will get 'OK' response even when there's no DEA available to run a user's APP. This will cause 0% health or 50% on cf's side without any clue to debug.

I think it's better to raise error in CC in order to tell the user what's wrong in CLI, rather than log the error silently inside the system.