Ignore connection attempts while server is shutting down

Ignore connection attempts while server is shutting down

Currently we still allow clients to connect while the server is waiting
to shut down. This window is very small (2s) and is only used when
explicit-exit-notify is enabled on the server side.

The chance of a client connecting during this time period is very low
unless someone puts something stupid like --connect-retry 1 3 into his/her
client config and forces the client to reconnect during this time period.

Github: OpenVPN/openvpn#189

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20221208153129.1207228-1-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg25638.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>