fix ping path

Author: axos88

templates/pool.conf.erb

@@ -253,7 +253,7 @@ pm.status_path = <%= @status_path %>
 ;       may conflict with a real PHP file.
 ; Default Value: not set
 <% if @ping_path %>
-ping_path = <%= @ping_path %>
+ping.path = <%= @ping_path %>
 <% else %>
 ;ping.path = /ping
 <% end %>