4840. [test] Add tests to cover fallback to using ZSK on inactive

KSK. [RT #46787]

bin/tests/system/autosign/ns3/inacksk2.example.db.in

@@ -0,0 +1,21 @@
+; Copyright (C) 2017  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/.
+
+$TTL 300	; 5 minutes
+@			IN SOA	mname1. . (
+				1          ; serial
+				20         ; refresh (20 seconds)
+				20         ; retry (20 seconds)
+				1814400    ; expire (3 weeks)
+				3600       ; minimum (1 hour)
+				)
+			NS	ns
+ns			A	10.53.0.3
+
+a			A	10.0.0.1
+b			A	10.0.0.2
+d			A	10.0.0.4
+x			CNAME	a