PR 22951, 2.0.x ProxyErrorOverride + 302 response = bad C-L

[Eric Covener <co...@gmail.com>]

The fix for http://issues.apache.org/bugzilla/show_bug.cgi?id=22951
was proposed for backport to 2.0.x and later pulled.

I added a simple config/results and some info to the PR, I don't think
the lack of support for cookies warrants shelving the backport.

Essentially ap_discard_request_body() is called after
reading/fowarding to output filters of the response from the origin
server in the case of some (302) status codes, causing confusion for
keepalive clients as we tack on our ErrorDocument.

2.2+ is more conservative about when it reads the response and sends
to output filters.

(1-line patch attached to PR)

-- 
Eric Covener
covener@gmail.com