Fix client crash on double PUSH_REPLY.

Introduce an extra bool variable c2.pulled_options_md5_init_done to
keep track of md5_init state of pulled_options_state - avoid accessing
uninitialized state when a second PUSH_REPLY comes in (which only happens
under very particular circumstances).

Bug tracked down by Arne Schwabe <arne@rfc2549.rrg>.

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: 20121225124856.GT22465@greenie.muc.de
URL: http://article.gmane.org/gmane.network.openvpn.devel/7216
Signed-off-by: David Sommerseth <davids@redhat.com>
(cherry picked from commit 1978db4b9657f0db134f1deaeb1e8400bf6a033e)