Move the check of the Expect request header field after the hook

for ap_post_read_request, since that is the only opportunity for
modules to handle Expect extensions.

Obtained from: apache-1.3


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@97765 13f79535-47bb-0310-9956-ffa450edef68