Add idempotency test to test_ldap_group

functional/test_ldap_group.yml

@@ -23,6 +23,12 @@
     - assert: { that: "{{ ldap_module.changed }} == True" }
     - assert: { that: "{{ ldap_module.rc }} == 0" }
 
+    - name: ldap configuration is idempotent
+      hashivault_auth_ldap:
+        ldap_url: ldap://localhost
+      register: ldap_module_idempotent
+    - assert: { that: "{{ ldap_module_idempotent.changed }} == False" }
+
     - name: remove ldap group
       hashivault_ldap_group:
         name: test