Remove WSU DNS from default setup

In 4a5101516, I added WSU nameservers to make DNS lookups on campus go faster for a few things. Not entirely sure why I thought that was a great idea. The commit message even mentions how we'll need to abstract it.

We should continue to use Google DNS by default, as it should be stable enough to route us where we need to go.

In the future, we'll want to abstract this a bit and allow DNS inside the VM to be a customizable thing. This would allow other orgs (and us) to choose.