Check that there is console output / a login prompt to make sure getty works

[travier]

Feature Request

See: coreos/fedora-coreos-tracker#1758

Make sure that users can interact with the console and login.

Desired Feature

N/A

Example Usage

N/A

Other Information

N/A

[Prashanna313]

Interested to pick

[jlebon]

Probably simplest for this is to add it to the list of console checks we do (i.e. add to the consoleChecks array in harness.go). Though currently that checks for bad things; we'd need to add another field to the struct to invert the polarity.

Feels weird to check on every test, though at the same time, it's very rare the cases where we don't expect a login prompt. Probably want to add a skip tag too if there are cases where indeed we don't (I know that happens in one of the testiso scenarios, but not in the primary kola run AFAIK).