BUG/MAJOR: mux-h1: Wake SC to perform 0-copy forwarding in CLOSING state

BUG/MAJOR: mux-h1: Wake SC to perform 0-copy forwarding in CLOSING state

When the mux is woken up on I/O events, if the zero-copy forwarding is
enabled, receives are blocked. In this case, the SC is woken up to be able
to perform 0-copy forwarding to the other side. This works well, except for
the H1C in CLOSING state.

Indeed, in that case, in h1_process(), the SC is not woken up because only
RUNNING H1 connections are considered. As consequence, the mux will ignore
connection closure. The H1 connection remains blocked, waiting for the
shutdown timeout. If no timeout is configured, the H1 connection is never
closed leading to a leak.

This patch should fix leak reported by Damien Claisse in the issue #2697. It
should be backported as far as 2.8.