Merge r1584078 from trunk:

try to clarify that "onsuccess" is for anything but locally-generated errors,
the module behavior and the doc are equally painful for users.




git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1584079 13f79535-47bb-0310-9956-ffa450edef68