BUG/MINOR: cache: Fully consume large requests in the cache applet

BUG/MINOR: cache: Fully consume large requests in the cache applet

In the cache applet (in HTX and legacy HTTP), when an cached object is sent to a
client, the request must be consumed. It is done at the end, after all the
response was copied into the channel's buffer. But only outgoing data at time
the applet is called are consumed. Then the applet is closed. If a request with
a huge body is sent, an error is triggerred because a SHUTW is catched on an
unfinished request.

Now, we consume request data as soon as possible and we do it until the end. In
fact, we don't try to shutdown the request's channel for write anymore.

This patch must be backported to 1.9 after some observation period.