Check that duplicate control sockets are caught

bin/tests/system/checkconf/bad-controls-duplicate.conf

@@ -0,0 +1,30 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0.  If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+key rndc-key {
+	algorithm "hmac-sha256";
+        secret "xxxxxxxxxxxxxxxxxxxxxxxx";
+};
+
+key ddns-key {
+	algorithm "hmac-sha256";
+        secret "yyyyyyyyyyyyyyyyyyyyyyyy";
+};
+
+controls {
+	inet 127.0.0.1 port 953 allow { 127.0.0.1; } keys { "rndc-key"; };
+};
+
+controls {
+	inet 127.0.0.1 allow { 127.0.0.1; } keys { ddns-key; };
+};