Add checks for external-key-managements

Add checks for external-key-managements

Commit 4806cc102655f1a829d656f6deb83e5953c5eab2 fixed only part of the
problem. Since it removed the filename either the magic filename has to be
resurrected or all checks against priv_key_file need to take to check for
MF_EXTERNAL_KEY as well. This patch implements the extra checks

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: David Sommerseth <davids@redhat.com>
Message-Id: 1347287973-12398-1-git-send-email-arne@rfc2549.org
URL: http://article.gmane.org/gmane.network.openvpn.devel/7046
Signed-off-by: David Sommerseth <davids@redhat.com>