Fix commands for using experimental kubeadm control plane (#5006)

roles/kubernetes/kubeadm/tasks/kubeadm_etcd_node.yml

@@ -3,8 +3,13 @@
   command: >-
     {{ bin_dir }}/kubeadm init phase
     --config {{ kube_config_dir }}/kubeadm-config.yaml
-    upload-certs --experimental-upload-certs
+    upload-certs
-    {% if kubeadm_certificate_key is defined %}
+    {% if kubeadm_version is version('v1.15.0', '<') %}
+    --experimental-upload-certs
+    {% else %}
+    --upload-certs
+    {% endif %}
+    {% if kubeadm_certificate_key is defined and kubeadm_version is version('v1.15.0', '<') %}
     --certificate-key={{ kubeadm_certificate_key }}
     {% endif %}
   register: kubeadm_upload_cert

roles/kubernetes/master/tasks/kubeadm-setup.yml

@@ -113,7 +113,7 @@
     {% if kubeadm_version is version('v1.14.0', '>=') %}
     {% if kubeadm_version is version('v1.15.0', '<') %}
     --experimental-upload-certs
-    {% if kubeadm_certificate_key is defined %}
+    {% if kubeadm_certificate_key is defined and kubeadm_version is version('v1.15.0', '<') %}
     --certificate-key={{ kubeadm_certificate_key }}
     {% endif %}
     {% else %}