when httpd is invoked without any -k option, mpm_common never registers ap_signal_server, which causes main() in server/main.c to continue through to startup-style processing without trying to look for an old pidfile. e.g. apachectl -f conf/httpd.conf sleep 2 apachectl -f conf/httpd.conf vs. any of the normal forms (single apachectl positional argument, or trailing -k start). Possible solutions would be to treat lack of -k arg even more like "start" and register signal_server, or blow up in the rewrite args hook (and check its return value) when no -k at all is present (maybe this in trunk?).
r1039989 in trunk checks the pidfile when this implied -k start is being used.
not backporting