Update timeout algorithm in free_proc_chain. Try polling the existing subprocess

a few times before going into a 3 second sleep. Often we find that the subprocess
will exit within milliseconds.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@97500 13f79535-47bb-0310-9956-ffa450edef68