gen_certs_script: refactor using stdin (Ansible 2.4+)
gen_certs_script: refactor using stdin (Ansible 2.4+)

Atoms/kubespray,Atoms/kubespray,kubernetes-incubator/kargo,kubespray/kargo,insequent/kargo,kubernetes-sigs/kubespray,kubernetes-incubator/kargo,Atoms/kubespray,kubespray/kargo,Atoms/kubespray,kubernetes-incubator/kubespray,kubernetes-sigs/kubespray,kubernetes-sigs/kubespray,insequent/kargo,kubernetes-sigs/kubespray,kubernetes-incubator/kubespray