Issue #2157017 by sun, rfay: DrupalHTTPRequestTestCase breaks on php-fpm [testbot PHP 5.4 blocker].

PR for https://github.com/backdrop/backdrop-issues/issues/222
Looks like the $user and $pw variables should be printed out here instead of the `$_SERVER['PHP_AUTH` equivalents. The bug itself seems like it was already fixed in Backdrop, this just updates the test callback. I can fix this in the merge.