Do not use ‘yes/no’ for boolean values (#11472)

Consistent boolean values in ansible playbooks

contrib/os-services/roles/prepare/tasks/main.yml

@@ -10,7 +10,7 @@
     systemd_service:
       name: firewalld
       state: stopped
-      enabled: no
+      enabled: false
     when:
       "'firewalld.service' in services and services['firewalld.service'].status != 'not-found'"
 
@@ -18,6 +18,6 @@
     systemd_service:
       name: ufw
       state: stopped
-      enabled: no
+      enabled: false
     when:
       "'ufw.service' in services and services['ufw.service'].status != 'not-found'"