kadm5/kadmin: Add read-only mode

Now we can have read-only kadmind instances.

lib/kadm5/rename_c.c

@@ -47,7 +47,7 @@ kadm5_c_rename_principal(void *server_handle,
     int32_t tmp;
     krb5_data reply;
 
-    ret = _kadm5_connect(server_handle);
+    ret = _kadm5_connect(server_handle, 1 /* want_write */);
     if (ret)
 	return ret;