Merge r451575, r451582 from trunk:

Enable retry=0 for the worker.
This allows to have an option to always retry
the workers in error state instead using a
specified time.

Move new struct member to the end of the struct,
so we can keep the compatibility.
Submitted by: mturk
Reviewed by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@576910 13f79535-47bb-0310-9956-ffa450edef68