Fix use-after-free with EVP_CIPHER_free

Fix use-after-free with EVP_CIPHER_free

In many scenarios the context will still have a reference to the cipher, so
this use-after-free does not explode but it is still wrong.

Change-Id: I59002d6613eaef36d5a47b20b56073e399cfa1df
Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Antonio Quartulli <a@unstable.cc>
Message-Id: <20230601095721.4065834-1-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26735.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 13f5e615310ea64ab69f521e622a10f2d0ad3f4e)