OS/2: Add clean-up to stop children taking the accept mutex with them to their

grave. When an OS/2 mutex's owner dies the mutex becomes invalid, causing the
error "OS2SEM: Error 105 getting accept lock. Exiting!"

PR: 4505


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@83377 13f79535-47bb-0310-9956-ffa450edef68