make 'explicit-exit-notify' pullable again

Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <519F5ED0.4070109@nikhef.nl>
URL: http://article.gmane.org/gmane.network.openvpn.devel/7605

Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 49f714942d5afd5f274aea52c790c896babc8c05)