Improve PolarSSL key_state_read_{cipher, plain}text messages

Improve PolarSSL key_state_read_{cipher, plain}text messages

Instead of logging the fact that an error occured, log the error code and
description (when available in the PolarSSL build).

Signed-off-by: Joachim Schipper <joachim.schipper@fox-it.com>
Acked-by: Adriaan de Jong <dejong@fox-it.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1363942465-3251-3-git-send-email-steffan.karger@fox-it.com>
URL: http://article.gmane.org/gmane.network.openvpn.devel/7440
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 0219f115f3a2711d5c51457d6e97d6930916653b)