mod_proxy: Keep connection alive on addressTTL expiry if the DNS didn't change.

mod_proxy: Keep connection alive on addressTTL expiry if the DNS didn't change.

* modules/proxy/proxy_util.c(address_cleanup):
  Rename to conn_cleanup() since it also closes the socket, and run
  socket_cleanup() first to avoid dangling conn->sock->remote_addr.

* modules/proxy/proxy_util.c(ap_proxy_determine_address):
  Compare the new address with the old one and keep the socket alive
  if it did not change.

Follow up to r1918410.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1918412 13f79535-47bb-0310-9956-ffa450edef68