Simplify balancer-manager XSS protection, no functional change:

* modules/proxy/mod_proxy_balancer.c (balancer_process_balancer_worker):
  Drop the ok2change parameter, which makes the function a noop, and
  require the function is not called for that case.
  (balancer_handler): Only call balancer_process_balancer_worker if
  the nonce matches.  Simplify call to balancer_display_page. 

Github: closes #174


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1887144 13f79535-47bb-0310-9956-ffa450edef68
