MINOR: httpclient: Don't limit data transfer to 1024 bytes

MINOR: httpclient: Don't limit data transfer to 1024 bytes

For debug purpose, no more 1024 bytes were copied at a time. But there is no
reason to keep this limitation. Thus, it is removed.

This patch may be backported to 2.5.

(cherry picked from commit fc5912914b320debad432c668b810170f6fd559a)
Signed-off-by: William Lallemand <wlallemand@haproxy.org>