Alias ADAPTER_DOMAIN_SUFFIX to DOMAIN

Alias ADAPTER_DOMAIN_SUFFIX to DOMAIN

ADAPTER_DOMAIN_SUFFIX is an openvpn3 replacement for
DOMAIN, which is used there for split-dns. This option is pushed
by modern Access Server.

This change improves compatibility between OpenVPN
community client and Access Server.

Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20200922100021.20329-1-lstipakov@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg21107.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit d6720203fa9ba446497798a284c17093b92de1dc)