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/node/templates/kubelet.env.v1beta1.j2

@@ -11,24 +11,12 @@ KUBELET_HOSTNAME="--hostname-override={{ kube_override_hostname }}"
 --bootstrap-kubeconfig=/etc/kubernetes/bootstrap-kubelet.conf \
 --config={{ kube_config_dir }}/kubelet-config.yaml \
 --kubeconfig={{ kube_config_dir }}/kubelet.conf \
-{% if kube_version is version('v1.8', '<') %}
---require-kubeconfig \
-{% endif %}
-{% if kube_version is version('v1.12.0', '<') %}
---cadvisor-port={{ kube_cadvisor_port }} \
-{% endif %}
 {# end kubeadm specific settings #}
 --pod-infra-container-image={{ pod_infra_image_repo }}:{{ pod_infra_image_tag }} \
-{% if container_manager == 'docker' and kube_version is version('v1.12.0', '<') %}
---docker-disable-shared-pid={{ kubelet_disable_shared_pid }} \
-{% endif %}
 {% if container_manager != 'docker' %}
 --container-runtime=remote \
 --container-runtime-endpoint={{ cri_socket }} \
 {% endif %}
-{% if kube_version is version('v1.8', '<') %}
---experimental-fail-swap-on={{ kubelet_fail_swap_on|default(true)}} \
-{% endif %}
 {% if dynamic_kubelet_configuration %}
 --dynamic-config-dir={{ dynamic_kubelet_configuration_dir }} \
 {% endif %}