kernel-netlink: Use address labels instead of deprecation for IPv6 virtual IPs

kernel-netlink: Use address labels instead of deprecation for IPv6 virtual IPs

In order to avoid that the kernel uses virtual tunnel IPs for traffic
over physical interfaces we previously deprecated the virtual IP.  While
this is working it is not ideal.  This patch adds address labels for
virtual IPs, which should force the kernel to avoid such addresses to
reach any destination unless there is an explicit route that uses it as
source address.