Don't just hardcode 30 seconds as the poll timeout.

* modules/proxy/mod_proxy_fcgi.c
  (dispatch): Use the worker timeout for our polls, falling back to the
   old behavior of 30 seconds if there is no worker timeout set.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/fcgi-proxy-dev@383292 13f79535-47bb-0310-9956-ffa450edef68