Enable disablereuse option in Zaqar proxy backend

Modify the Zaqar mod_proxy backend to use use the parameter
disablereuse=On, disabling the ability to reuse connections to the
proxy backend.  This is necessary to prevent reuse of connections by
mod_proxy to the backend Zaqar WebSocket server when the Zaqar
WebSocket server closes the socket on its own, that mod_proxy
occasionally expects to be open.  This creates a new connection with
every request.

Change-Id: Id5f22d8682805566eadd8205a5aa88524ce94b80
Closes-Bug: #1803422
(cherry picked from commit d4c98bd2c6)

manifests/ui.pp

@@ -151,8 +151,9 @@ class tripleo::ui (
     fallbackresource => '/index.html',
     proxy_pass       => [
     {
-      'path' => '/zaqar',
-      'url'  => $endpoint_proxy_zaqar
+      'path'   => '/zaqar',
+      'url'    => $endpoint_proxy_zaqar,
+      'params' => { 'disablereuse' => 'On' }
     },
     {
       'path'         => '/keystone',