Do not set nl socket buffer size

Do not set nl socket buffer size

libnl increases the sizes we pass to 8192 anyway. Currently when we have
a lot of events queued we might run into a NLE_NOMEM message and that
terminates the server. So rather let the kernel decide the buffer sizes.

Signed-off-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20221224194253.3202231-7-arne@rfc2549.org>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg25789.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit b2ca179ce2678115c3a61fd3f843c64c1d059fbc)