Fix some ansible-lint complaints.

roles/ldap/tasks/main.yml

@@ -1,6 +1,7 @@
 ## Install and configure slapd.
 ---
-- fail: msg="The machine's domain must not be empty."
+- name: check if domain name is available
+  fail: msg="The machine's domain must not be empty."
   when: ansible_domain | length == 0
 
 - name: check if slapd is already set up
@@ -87,6 +88,6 @@
   firewalld:
     zone: internal
     service: ldap
-    permanent: yes
-    immediate: yes
+    permanent: true
+    immediate: true
     state: enabled