BUG/MEDIUM: lua: Fully consume large requests when an HTTP applet ends

BUG/MEDIUM: lua: Fully consume large requests when an HTTP applet ends

In Lua, when an HTTP applet ends (in HTX and legacy HTTP), we must flush
remaining outgoing data on the request. But only outgoing data at time the
applet is called are consumed. 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.