Use on-marked-down shutdown-sessions for redis haproxy conf

The problem we have with redis can be described as follows:
- Connection is made to redis via haproxy, where haproxy directs to one redis node
- That chosen redis node fails and a new redis node gets promoted
- HAProxy will send *new* connections to redis to the newly promoted
  redis server, but you still have a session active (ie. that has not hit
  timeout), so haproxy will attempt to use that connection.

By using 'on-marked-down shutdown-sessions' we make sure we close
old existing sessions when the redis master node changes.

Closes-Bug: #1742086
Tested-By: Marian Krcmarik <mkrcmari@redhat.com>

Change-Id: Ia4d8c27057ee2de9e49e4358aa069571d1c952a9

manifests/haproxy.pp

@@ -1432,7 +1432,7 @@ class tripleo::haproxy (
       ports             => '6379',
       ipaddresses       => hiera('redis_node_ips', $controller_hosts_real),
       server_names      => hiera('redis_node_names', $controller_hosts_names_real),
-      options           => $haproxy_member_options,
+      options           => union($haproxy_member_options, ['on-marked-down shutdown-sessions']),
     }
     if $manage_firewall {
       include ::tripleo::firewall