Actually use the secret when generating nonces.

This change may cause problems if used with round robin load balancers.
Before it is backported, we should add a directive to use a user specified
secret.

PR: 54637


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1492395 13f79535-47bb-0310-9956-ffa450edef68