Guh, this is complicated.
Fixes#4640
This also follows up on #4398 (reverting it) which made a change that technically worked, but was incorrect. It changed the condition in `hostsFromKeysNotHTTP` from `&&` to `||`, but then the function no longer did what its name said it would do, and it would return hosts even if they were marked with `http://`, if they used a non-HTTP port. That wasn't the intent of it. The test added in there was kept though, because it is a valid usecase.
The actual fix is to check _earlier_ whether all the addresses explicitly have `http://`, and if so we can short circuit and skip considering the rest.