Use K8s 1.15 (#4905)

* Use K8s 1.15

* Use Kubernetes 1.15 and use kubeadm.k8s.io/v1beta2 for
  InitConfiguration.
* bump to v1.15.0

* Remove k8s 1.13 checksums.

* Update README kubernetes version 1.15.0.

* Update metrics server 0.3.3 for k8s 1.15

* Remove less than k8s 1.14 related code

* Use kubeadm with --upload-certs instead of --experimental-upload-certs due to depricate

* Update dnsautoscaler 1.6.0

* Skip certificateKey if it's not defined

* Add kubeadm-conftolplane.v2beta2 for k8s 1.15 or later

* Support kubeadm control plane for k8s 1.15

* Update sonobuoy version 0.15.0 for k8s 1.15

roles/kubernetes/master/tasks/kubeadm-secondary-experimental.yml

@@ -30,8 +30,13 @@
   command: >-
     {{ bin_dir }}/kubeadm init phase
     --config {{ kube_config_dir }}/kubeadm-config.yaml
-    upload-certs --experimental-upload-certs
-    {% if kubeadm_certificate_key is defined %}
+    upload-certs
+    {% 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
@@ -52,7 +57,7 @@
     {{ bin_dir }}/kubeadm join
     --config {{ kube_config_dir }}/kubeadm-controlplane.yaml
     --ignore-preflight-errors=all
-    {% 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 %}
   register: kubeadm_join_control_plane