Add support for zookeeper timeout

Change-Id: I743bfa28d2faaa93bba6fc975d575696bd8a5a70

manifests/init.pp

@@ -30,6 +30,7 @@ class zuul (
   $zuul_ssh_private_key = '',
   $layout_file_name = 'layout.yaml',
   $zookeeper_hosts = '127.0.0.1:2181',
+  $zookeeper_session_timeout = undef,
   $tenant_file_name = 'main.yaml',
   $url_pattern = '',
   $status_url = "https://${::fqdn}/",

templates/zuulv3.conf.erb

@@ -34,6 +34,9 @@ status_url=<%= @status_url %>
 
 [zookeeper]
 hosts=<%= @zookeeper_hosts %>
+<% if @zookeeper_session_timeout != nil -%>
+session_timeout=<%= @zookeeper_session_timeout %>
+<% end -%>
 
 [merger]
 git_dir=/var/lib/zuul/git