This addresses some assumptions made by systemd about having multiple
routing table support in the kernel. systemd-networkd will try and
provision mutliple routing tables + policies and will silently break
neighbor advertisement responses due to policy configurations on a
single table.

It also adds support for SLAAC based router settings and faster
duplicate address detection.
Signed-off-by: William A. Kennington III <wak@google.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>