BUG/MINOR: http-ana: Reset request analysers on a response side error

BUG/MINOR: http-ana: Reset request analysers on a response side error

When an error occurred on the response side, request analysers must be reset. At
this stage, only AN_REQ_HTTP_XFER_BODY analyser remains, and possibly
AN_REQ_FLT_END, if at least one filter is attached to the stream. So it is safe
to remove the AN_REQ_HTTP_XFER_BODY analyser. An error was already handled and a
response was already returned to the client (or it was at least scheduled to be
sent). So there is no reason to continue to process the request payload. It may
cause some troubles for the filters because when an error occurred, data from
the request buffer are truncated.

This patch must be backported as far as 1.9, for the HTX part only. I don't know
if the legacy HTTP code is affected.

(cherry picked from commit e58c0002ff7dc1f88990171810f268ae26d0cf99)
[wt: context adjustments since this place was already touched by b8a5371a]
Signed-off-by: Willy Tarreau <w@1wt.eu>