permission: Fix idempotency issues for DN parameters

The parameters

- subtree (ipapermlocation)
- target (ipapermtarget)
- targetto (ipapermtargetto)
- targetfrom (ipapermtargetfrom)

have not been idempotent as the result returned from permission_show was
a DN and not a string.

The find_permission function has been exetended to convert the values
for these parameters to strings.

Fixes: #1257

plugins/modules/ipapermission.py

@@ -154,7 +154,7 @@ RETURN = """
 
 
 from ansible.module_utils.ansible_freeipa_module import \
-    IPAAnsibleModule, compare_args_ipa
+    IPAAnsibleModule, compare_args_ipa, to_text
 
 
 def find_permission(module, name):
@@ -164,7 +164,12 @@ def find_permission(module, name):
     except Exception:  # pylint: disable=broad-except
         # An exception is raised if permission name is not found.
         return None
-    return _result["result"]
+    _res = _result["result"]
+    for param in ["ipapermlocation", "ipapermtarget", "ipapermtargetto",
+                  "ipapermtargetfrom"]:
+        if param in _res:
+            _res[param] = [to_text(elem) for elem in _res[param]]
+    return _res
 
 
 def gen_args(right, attrs, bindtype, subtree,