Merge r506621 from trunk:

* Save the key we generate during our first run of cache_generate_key_default
  on each request in the request_config. During consecutive runs of
  cache_generate_key_default during processing the request we restore it
  from there as we might not be able to generate the same key again as
  the ingredients used to compose the key might have changed and we constantly
  must use a key that could be generated during the quick handler phase.

PR: 41475

Submitted by: rpluem
Reviewed by: rpluem, jerenkrantz, jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@539112 13f79535-47bb-0310-9956-ffa450edef68