Disable notifies for mirror zones unless also-notify is used

Since the mirror zone feature is expected to mostly be used for the root
zone, prevent slaves from sending NOTIFY messages for mirror zones by
default.  Retain the possibility to use "also-notify" as it might be
useful in certain cases.

bin/tests/system/mirror/tests.sh

@@ -347,5 +347,12 @@ grep "; Transfer failed" dig.out.ns3.test$n > /dev/null || ret=1
 if [ $ret != 0 ]; then echo_i "failed"; fi
 status=`expr $status + $ret`
 
+n=`expr $n + 1`
+echo_i "checking that notifies are disabled by default for mirror zones ($n)"
+ret=0
+grep "initially-unavailable.*sending notifies" ns3/named.run > /dev/null && ret=1
+if [ $ret != 0 ]; then echo_i "failed"; fi
+status=`expr $status + $ret`
+
 echo_i "exit status: $status"
 [ $status -eq 0 ] || exit 1