Pull apart swift haproxy health checker

[OpenStack Infra]

https://review.openstack.org/255892
Dear bug triager. This bug was created since a commit was marked with DOCIMPACT.

commit 69390d7d16403defee33caee10e3a990a7c3b795
Author: Michael Polenchuk <email address hidden>
Date: Thu Dec 10 16:55:21 2015 +0300

    Pull apart swift haproxy health checker

    Setup custom script checker with additional auth endpoint availability
    scan if swift proxy listens to the same ip address with storage daemons
    otherwise use default internal health check method.

    Also introduce the following haproxy options:
    * <spread-checks>
      add some randomness in the check interval to avoid sending
      health checks to servers at exact interspaces.
    * <dontlognull>
      disable logging of null connections as these can pollute the logs.
    * <tcp-smart-accept, tcp-smart-connect>
      performance tweak, saving one ACK packet during the
      accept/connect sequence.

    DocImpact
    Change-Id: I70ebdc595e85294559d33cc03d4221a738b0bbc5
    Closes-Bug: #1516978