Lowercase instance and org name when computing instance DNS

[elprans]

Nebula switched to doing this, and so the clients must follow.

[tailhook]

I think we should lowercase them in the constructor of InstanceName so that comparison works well if/when we need it.

[elprans]

I think it's better to lowercase in constructor. This will make comparison and collections over instance names work fine. Unfortunately, this also means hiding the internal structure for the type.

Yes, but that's a much bigger change. Let's merge this fix and then follow up on a general cleanup/generalization of instance handling.