Password expiration tests do not reliably pass

Two of the password expiration test methods pass or fail depending on luck.

The problem is they check for expiration emails for a particular user using assertMail(), but the test methods do not account for the fact that the admin (uid=1) password also expires and generates expiration emails. How the expiration emails for the test user and admin are ordered in the drupal_test_email_collector variable checked by assertMail() is undefined.

Patch forthcoming.