BUG/MEDIUM: mux-h1: Always release H1C if a shutdown for writes was reported

BUG/MEDIUM: mux-h1: Always release H1C if a shutdown for writes was reported

We must take care of this when the stream is detached from the
connection. Otherwise, on the server side, the connexion is inserted in the list
of idle connections of the session. But when reused, because the shutdown for
writes was already catched, nothing is sent to the server and the session is
blocked with a freezed connection.

This patch must be backported to 2.0 and 1.9. It is related to the issue #136
reported on Github.