pipelined test: we no longer have -Tdelay option, use a python proxy that delays packets as a workaround

bin/tests/system/pipelined/prereq.sh

@@ -0,0 +1,29 @@
+#!/bin/sh
+#
+# Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+#
+# 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 http://mozilla.org/MPL/2.0/.
+#
+# See the COPYRIGHT file distributed with this work for additional
+# information regarding copyright ownership.
+
+SYSTEMTESTTOP=..
+. $SYSTEMTESTTOP/conf.sh
+
+if test -n "$PYTHON"
+then
+    if $PYTHON -c "import dns" 2> /dev/null
+    then
+        :
+    else
+        echo_i "This test requires the dnspython module." >&2
+        exit 1
+    fi
+else
+    echo_i "This test requires Python and the dnspython module." >&2
+    exit 1
+fi
+
+exit 0