Backport http://svn.apache.org/r1661913

ab: Add missing longest request (100%) to CSV export. PR57614.

Submitted by: ylavic
Reviewed by: covener, minfrin


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1663405 13f79535-47bb-0310-9956-ffa450edef68