NodeLocalDNS addon listens on both DNS_SERVER_IP as well as LOCAL_DNS_IP. So cluster-dns flag can continue to be DNS_SERVER_IP in all cases.
Documented the various variables in the yaml.
The bug seems to be currently dormant but I managed to trigger it in
some manual tests.
When the bug is triggered it appends empty --prune-whitelist without any
value which in turn can capture the next flag and can cause addon
manager to fail.
E.g. when bug is not triggered the kubectl command looks like this
```
kubectl ... --prune-whitelist extensions/v1beta1/Ingress --recursive ...
```
When it's triggered it will be
```
kubectl ... --prune-whitelist --recursive ...
```
which will capture the --recursive flag and will make addon-manager to
fail as there are no yamls in the top directory.
Without this it fails after deployments were switched from
extensions to apps with
```
E0902 11:25:51.197420 1 reflector.go:283] github.com/kubernetes-incubator/cluster-proportional-autoscaler/pkg/autoscaler/k8sclient/k8sclient.go:96: Failed to watch *v1.Node: unknown (get nodes)
E0902 11:25:53.118490 1 reflector.go:283] github.com/kubernetes-incubator/cluster-proportional-autoscaler/pkg/autoscaler/k8sclient/k8sclient.go:96: Failed to watch *v1.Node: unknown (get nodes)
E0902 11:25:54.997493 1 reflector.go:283] github.com/kubernetes-incubator/cluster-proportional-autoscaler/pkg/autoscaler/k8sclient/k8sclient.go:96: Failed to watch *v1.Node: unknown (get nodes)
E0902 11:25:57.097423 1 reflector.go:283] github.com/kubernetes-incubator/cluster-proportional-autoscaler/pkg/autoscaler/k8sclient/k8sclient.go:96: Failed to watch *v1.Node: unknown (get nodes)
E0902 11:25:59.097417 1 reflector.go:283] github.com/kubernetes-incubator/cluster-proportional-autoscaler/pkg/autoscaler/k8sclient/k8sclient.go:96: Failed to watch *v1.Node: unknown (get nodes)
I0902 11:25:59.697325 1 k8sclient.go:221] Falling back to extensions/v1beta1, error using apps/v1: deployments.apps "calico-typha" is forbidden: User "system:serviceaccount:kube-system:typha-cpha" cannot get resource "deployments/scale" in API group "apps" in the namespace "kube-system"
E0902 11:25:59.699833 1 autoscaler_server.go:120] Update failure: the server could not find the requested resource
```
Ref. https://github.com/kubernetes/test-infra/pull/13709
