Use RSA_meth_free instead of free

Use RSA_meth_free instead of free

- RSA_meth_new allocates memory for the name string
  and must be released using RSA_meth_free

Signed-off-by: Selva Nair <selva.nair@gmail.com>
Acked-by: Emmanuel Deloget <logout@free.fr>
Acked-by: Steffan Karger <steffan.karger@fox-it.com>
Message-Id: <1515884446-27152-1-git-send-email-selva.nair@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg16207.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 508741c1cf99b8a24205601800fa5056c6d0192b)