Move NCP saving and restore to the prepush restore code

Move NCP saving and restore to the prepush restore code

This unifies save/restoring options that might be changed by a push
from the server. It also removes using the context_1 to store something
that is not related to a SIGHUP lifetime.

Patch v2: rebase on master.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Antonio Quartulli <antonio@openvpn.net>
Message-Id: <20210317160038.25828-2-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg21674.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>