Fix IPv6 host routes to LAN gateway on OpenSolaris

Fix IPv6 host routes to LAN gateway on OpenSolaris

The tun/tap routes need to be set with "metric 0", while this will
prevent routes to LAN gateways from being installed.  So, set metric 0
only if no other interface is requested...

(Note: OpenSolaris can not specify host+interface gateways, so we just
use the GW addresses - it seems to still work for fe80:: addresses,
however it is done internally.  NUD maybe?)

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <1441985627-14822-10-git-send-email-gert@greenie.muc.de>
URL: http://article.gmane.org/gmane.network.openvpn.devel/10092