When a site requires login, do not show "site is overloaded" banner, there is no anon access

[codinghorror (Jeff Atwood)]

@sam

Best we can do under extreme load, for “requires login” sites, is simply to render a blue screen saying “site is overloaded, try again later”. Would like to wait a bit before adding this and see 1 more complaint.

I think it’s safe to add this now… if a requires-login site is overloaded, adding more users isn’t going to improve things for them.