style: incorporate recommendations from ansible-lint

handlers/main.yml

site.yml

tasks/backup_ssh_hostkeys.yml

tasks/configure_autoupdate.yml

tasks/configure_bash.yml

tasks/configure_exim.yml

tasks/configure_glances.yml

tasks/configure_htop.yml

tasks/configure_logrotate.yml

tasks/configure_motd.yml

tasks/configure_ntp.yml

tasks/configure_package_repositories.yml

tasks/configure_persistent_journald_logging.yml

tasks/configure_postfix.yml

tasks/configure_root_shell.yml

tasks/configure_sar.yml

tasks/configure_ssh_keys.yml

tasks/configure_ssh_login.yml

tasks/configure_sudoers.yml

tasks/configure_swap.yml