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>