BUG/MEDIUM: sessions: Always pass the mux context as argument to destroy a mux

This bug was introduced by the commit 2444aa5b ("MEDIUM: sessions: Don't be
responsible for connections anymore."). In session_check_idle_conn(), when the
mux is destroyed, its context must be passed as argument instead of the
connection.

It is de 2.2-dev bug. No need to backport.
1 file changed