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

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

In the stats applet (in HTX and legacy HTTP), after a response is fully sent to
a client, the request is 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 for an unfinisehd
request.

Now, we consume request data 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. It should
probably be backported in prior versions too. But honnestly, with refactoring
on the connection layer and the stream interface in 1.9, it is probably safer
to not do so.