Fix internal and external traffic policy to be handled separately (so
that, in particular, services with Local internal traffic policy and
Cluster external traffic policy do not behave as though they had Local
external traffic policy as well.
Additionally, traffic to an `internalTrafficPolicy: Local` service on
a node with no endpoints is now dropped rather than being rejected
(which, as in the external case, may prevent traffic from being lost
when endpoints are in flux).
Just check that the actual IP:port of the filtered endpoints is
correct; using DeepEqual requires us to copy all the extra endpoint
fields (eg, ZoneHints, IsLocal) from endpoints to expectedEndpoints,
which just makes the test cases unnecessarily bigger.
The "node local endpoints, hints are ignored" test was not actually
enabling topology correctly, so it would have gotten the expected
result even if the code was wrong. (Which, FTR, it wasn't.)
1. Add API definitions;
2. Add feature gate and drops the field when feature gate is not on;
3. Set default values for the field;
4. Add API Validation
5. add kube-proxy iptables and ipvs implementations
6. add tests
