Add tests for DNSSEC sign statistics

This adds tests to the statschannel system test for testing if
the dnskey sign operation counters are incremented correctly.

It tests three cases:

1. A zone maintenance event where all the signatures that are about
   to expire are resigned.
2. A dynamic update event where the new RR and other relevant records
   (SOA, NSEC) are resigned.
3. Adding a standby key, that means the DNSKEY and SOA RRset are
   resigned.

bin/tests/system/statschannel/zones-json.pl

@@ -0,0 +1,30 @@
+#!/usr/bin/perl
+#
+# 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.
+
+# zones-json.pl:
+# Parses the JSON version of the dnssec sign stats for the
+# "dnssec" zone in the default view into a normalized format.
+
+use JSON;
+
+my $file = $ARGV[0];
+open(INPUT, "<$file");
+my $text = do{local$/;<INPUT>};
+close(INPUT);
+
+my $ref = decode_json($text);
+
+
+my $dnssecsign = $ref->{views}->{_default}->{zones}[0]->{"dnssec"};
+my $type = "dnskey sign operations ";
+foreach $key (keys %{$dnssecsign}) {
+    print $type . $key . ": ". $dnssecsign->{$key} ."\n";
+}