Allow IPv6 packets on INPUT
Allow IPv6 packets on INPUT

There are multiple things in a Kubernetes cluster that require to receive packets on the host network namespace:
- NodePort Services
- HostNetwork true pods
- Healthchecks endpoints
- ...

COS images use DROP as default policy and we were overriding it to ACCEPT everything by default in INPUT and FORWARD.
However, for IPv6 we will only accepting packets on FORWARD, this adds the missing rules to ACCEPT on INPUT too
GoogleCloudPlatform/netd,GoogleCloudPlatform/netd,GoogleCloudPlatform/netd