agent: Announce both IPv4 and IPv6 node address via node discovery
agent: Announce both IPv4 and IPv6 node address via node discovery

No real functional differences as the IPv6 node address is not used in the
datapath but it ensures that the IPv6 node address is listed in `cilium node
list`.

Signed-off-by: Thomas Graf <5f50a84c1fa3bcff146405017f36aec1a10a9e38@cilium.io>

cilium/cilium,cilium/cilium,tgraf/cilium,tgraf/cilium,tgraf/cilium,tklauser/cilium,tgraf/cilium,cilium/cilium,cilium-team/cilium,cilium/cilium,michi-covalent/cilium,tklauser/cilium,tklauser/cilium,tklauser/cilium,michi-covalent/cilium,michi-covalent/cilium,cilium-team/cilium,tgraf/cilium,michi-covalent/cilium,cilium/cilium,tgraf/cilium,michi-covalent/cilium,tklauser/cilium