Fix yamllint `document-start` occurrences.

galaxy.yml

meta/runtime.yml

molecule/resources/playbooks/prepare-common.yml

playbooks/dnszone/dnszone-all-params.yml

playbooks/dnszone/dnszone-present.yml

playbooks/host/host-member-certificate-absent.yml

playbooks/host/host-member-certificate-present.yml

playbooks/host/host-present-with-certificate.yml

roles/ipabackup/meta/main.yml

roles/ipabackup/vars/Fedora.yml

roles/ipabackup/vars/RedHat-7.yml

roles/ipabackup/vars/RedHat-8.yml

roles/ipabackup/vars/Ubuntu.yml

roles/ipabackup/vars/default.yml

roles/ipaclient/meta/main.yml

roles/ipaclient/vars/Debian.yml

roles/ipaclient/vars/Fedora-25.yml

roles/ipaclient/vars/Fedora-26.yml

roles/ipaclient/vars/RedHat-7.3.yml

roles/ipaclient/vars/RedHat-7.yml