Fixed skip of no ntp test

git-svn-id: https://nagiosplug.svn.sourceforge.net/svnroot/nagiosplug/nagiosplug/trunk@1468 f882894a-f735-0410-b71e-b25c423dba1c

plugins/t/check_ntp.t

@@ -38,7 +38,7 @@ SKIP: {
 }
 
 SKIP: {
-	skip "No bad NTP server defined", 1 unless $ntp_service;
+	skip "No bad NTP server defined", 1 unless $no_ntp_service;
 	$res = NPTest->testCmd(
 		"./check_ntp -H $no_ntp_service"
 		);