vrrp: unicast_peer addresses and VRRP instance MUST be of the same family

VRRP low-level framework create socket pool based on VRRP instance family. If
you are using unicast_peer, it is mandatory to use addresses of same family as
VRRP instance. You cant mix IPv4 and IPv6 addresses inside same unicast_peer block.
If you need to make it that way, you MUST create a VRRP instance per family,
eg: one with native_ipv6 for v6 unicast_peer and another for v4 unicast_peer.