Change httpd.pid placement to rel_runtimedir instead of rel_logfiledir.

With the standard apache layout, this changes nothing (since runtimedir ==
logfiledir), but for other layouts, this makes a lot more sense.

PR: 7841
Submitted by:   Andreas Hasenack <andreas@netbank.com.br>
Reviewed by:    Justin Erenkrantz


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@94606 13f79535-47bb-0310-9956-ffa450edef68