fix(ecmp_vip): check for nil nodename (#903)

While rare that NodeName is missing it is not guaranteed to exist by the
Kubernetes API (see link below). This retains checking via NodeName
first if it exists, but if it's nil rather than segfaulting it evaluates
the via IP address.

Fixes #781

https://github.com/cloudnativelabs/kube-router/blob/master/vendor/k8s.io/api/core/v1/types.go#L3487

Author: aauren

pkg/controllers/routing/ecmp_vip.go

@@ -436,8 +436,14 @@ func (nrc *NetworkRoutingController) nodeHasEndpointsForService(svc *v1core.Serv
 
 	for _, subset := range ep.Subsets {
 		for _, address := range subset.Addresses {
-			if *address.NodeName == nrc.nodeName {
-				return true, nil
+			if address.NodeName != nil {
+				if *address.NodeName == nrc.nodeName {
+					return true, nil
+				}
+			} else {
+				if address.IP == nrc.nodeIP.String() {
+					return true, nil
+				}
 			}
 		}
 	}