mpm_unix: Apache fails to start if previously crashed then restarted with

the same PID (e.g. in container).  PR 60261.

Proposed by: Val <valentin.bremond gmail.com>
Reviewed by: ylavic


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1766160 13f79535-47bb-0310-9956-ffa450edef68