Be more strict in console_login
    
    Because we use check_screen not assert_screen here, the match
    can actually fail, but the match_has_tag conditional can pass
    on the *previous* match, if that happened to also be matching
    on a console tag. We don't want that. Let's just make these
    into assert_screens to avoid it; I don't think there's any path
    where we're actually expecting this to work if those
    check_screens didn't match.
    
    Signed-off-by: Adam Williamson <awilliam@redhat.com>