configure.ac: fix SSL_OP_NO_TICKET check

Only check for SSL_OP_NO_TICKET if building with --enable-ssl and using
openssl. This fixes cross-compiling polarssl builds for Windows (where
pkg-config would find the system openssl library, but the cross compiler
would not have openssl for the target platform).

Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1403461119-21440-1-git-send-email-steffan@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8795
Signed-off-by: Gert Doering <gert@greenie.muc.de>