BUG/MEDIUM: connections: Make sure we're unsubscribe before upgrading the mux.

Just calling conn_force_unsubscribe() from conn_upgrade_mux_fe() is not
enough, as there may be multiple XPRT involved. Instead, require that
any user of conn_upgrade_mux_fe() unsubscribe itself before calling it.
This should fix upgrading a TCP connection to HTX when using SSL.

This should be backported to 2.0.

(cherry picked from commit 2ab3dada015e071f505554cf443bfc438ce863e5)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
3 files changed