Fix race condition dnssec-policy with views

When configuring the same dnssec-policy for two zones with the same
name but in different views, there is a race condition for who will
run the keymgr first. If running sequential only one set of keys will
be created, if running parallel two set of keys will be created.

Lock the kasp when running looking for keys and running the key
manager. This way, for the same zone in different views only one
keyset will be created.

The dnssec-policy does not implement sharing keys between different
zones.

bin/tests/system/kasp/ns4/example2.db.in

@@ -0,0 +1,22 @@
+; 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.
+
+$TTL 300
+@		IN	SOA  mname1. . (
+			1       ; serial
+			20      ; refresh (20 seconds)
+			20      ; retry (20 seconds)
+			1814400 ; expire (3 weeks)
+			3600    ; minimum (1 hour)
+			)
+
+			NS	ns4
+ns4			A	10.53.0.4
+
+view			TXT	"view2"