Merge r1649043 from trunk:

mod_proxy_ajp: Fix get_content_length().

clength in request_rec is for response sizes,
not request body size. It is initialized to 0,
so the "if" branch was never taken.

Submitted by: rjung
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1651096 13f79535-47bb-0310-9956-ffa450edef68