add ignore_errors to the kube-proxy deletion task (#5236)

When using cluster.yml or scale.yml to add/scale nodes in the existing
k8s cluster, the `kubeadm init` wouldn't run. As a result, kube-proxy
wouldn't be created, and therefore the kube-proxy deletion task would
fail, e.g. in the case where kube-router is used and "kube_proxy_remove"
is set to true. As a workaround, add ignore_errors to the kube-proxy
deletion task.

roles/kubernetes/kubeadm/tasks/main.yml

@@ -150,6 +150,8 @@
     - inventory_hostname == groups['kube-master']|first
     - kube_proxy_remove
     - kubeadm_discovery_address != kube_apiserver_endpoint | replace("https://", "")
+  # When scaling/adding nodes in the existing k8s cluster, kube-proxy wouldn't be created, as `kubeadm init` wouldn't run.
+  ignore_errors: true
   tags:
     - kube-proxy