Fix adding output of kubeadm to the admin.conf downloaded to the artifacts directory (#4696)

Fixes issue https://github.com/kubernetes-sigs/kubespray/issues/4695

roles/kubernetes/client/tasks/main.yml

@@ -66,7 +66,7 @@
     --apiserver-advertise-address {{ external_apiserver_address }}
     --apiserver-bind-port {{ external_apiserver_port }}
     {% if kubeadm_version is version('v1.14.0', '>=') %}
-    && cat {{ kube_config_dir }}/external_kubeconfig/admin.conf &&
+    >/dev/null && cat {{ kube_config_dir }}/external_kubeconfig/admin.conf &&
     rm -rf {{ kube_config_dir }}/external_kubeconfig
     {% endif %}
   environment: "{{ proxy_env }}"