When the server shuts down cleanly, it also removes the httpd.pid PID file.

This avoids the problem that apachectl cannot decide whether a "kill -0 pid"
failed because of permissions (or system restrictions) or because the pid
doesn't exist. Upon startup, an info msg is logged if an old PID file remains.

PR: 2947
Submitted by:	Charles Randall <crandall@matchlogic.com>
Reviewed by:	Martin Kraemer, Dean Gaudet


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@82047 13f79535-47bb-0310-9956-ffa450edef68