Plug memory leak if push is interrupted

Plug memory leak if push is interrupted

If a push is interrupted due to a timeout, c->c2.pulled_options_state is
never freed.  Fix that by always cleaning up any remaining pulled
options state when we close a connection.

This changes the mbedtls implementation of md_ctx_cleanup to actually
clean up the context, which was not needed earlier.

Signed-off-by: Steffan Karger <steffan.karger@fox-it.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1516194984-1540-1-git-send-email-steffan.karger@fox-it.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg16265.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 07036fd3c456ed4ebf1809d8d9f34941d42865d0)