Merge r1462269, r1463455 from trunk:

* Improve reusage of already resolved addresses to avoid unnecessary DNS lookups.

* Always try to reuse the address looked up for the worker if we are allowed to
  reuse the address. This saves DNS lookups.

Submitted by: rpluem
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1511313 13f79535-47bb-0310-9956-ffa450edef68