Hard coded syscall.AF_INET breaks ipv6 operation for ipvs destination list

[uablrek]

The hard-coded value is here;
https://github.com/docker/libnetwork/blob/d7b61745d16675c9f548b19f06fda80d422a74f0/ipvs/netlink.go#L425

This breaks the ipvs sync function in Kubernetes in ipv6-only configuration with proxy-mode=ipvs as described in this issue;
kubernetes/kubernetes#65006

[aojea]

@uablrek seems this was fixed by #2416

[thaJeztah]

ping @selansen @euanh looks like this can be closed