Merge r378032 from trunk:

  *) mod_proxy: Fix KeepAlives not being allowed and set to
     backend servers. PR38602. [Ruediger Pluem, Jim Jagielski]

Also, document previous patch:
  *) Correctly initialize mod_proxy workers, which use a
     combination of local and shared datasets. Adjust logging
     to better trace usage. PR38403. [Jim Jagielski]


Reviewed by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@390492 13f79535-47bb-0310-9956-ffa450edef68