mod_proxy_fcgi: prioritize the check for mayflush when using flushpackets

The mayflush variable should be checked before the rest
to avoid polling when not needed.

Suggested by Yann Ylavic on the dev@ mailing list.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1823886 13f79535-47bb-0310-9956-ffa450edef68