Fix regex to disregard locked accounts

[pyllyukko]

This way, accounts that have ":!!:" in shadow and have an entry in
"Password expires" field don't get flagged with "Result: password of
user XYZ has been expired" by AUTH-9288.

Fixes #362

[pyllyukko]

I'm still thinking whether this test should disregard locked accounts completely (e.g. :!!$6...).

I can add the commit to this same pull request if you agree, @mboelen?

Of course it can be unlocked by admin to re-enable the expired password, so maybe it's good to be aware of these kind of accounts. Admins can also remove the expired hash from shadow with passwd -d.

[mboelen]

Thanks, it has been merged. For now, let's leave the test like this. This way these accounts at least show up and the admin can take action.