SELINUX_CHILD: 'ret' argument of prepare_response() is always 0

both in current and pre- sssd-2.10.1 code. Let's make it explicit.

src/providers/ipa/selinux_child.c

@@ -414,7 +414,7 @@ int main(int argc, const char *argv[])
 
     sss_log_process_caps("Sending response");
 
-    ret = prepare_response(main_ctx, ret, &resp);
+    ret = prepare_response(main_ctx, EOK, &resp);
     if (ret != EOK) {
         DEBUG(SSSDBG_CRIT_FAILURE, "Failed to prepare response buffer.\n");
         goto fail;