refactor: ntp apps (#4333)

* updated nicecase function for ntp server and client app

* ntp applications refactoring

* removed agent for ntp-server: reported as not working

* removed ntpd from agent polling. thx @murrant

html/includes/functions.inc.php

@@ -73,8 +73,11 @@ function nicecase($item)
         case 'nfs-v3-stats':
             return 'NFS v3 Stats';
 
-        case 'ntpd':
-            return 'NTPD (Server)';
+        case 'ntp-client':
+            return 'NTP Client';
+
+        case 'ntp-server':
+            return 'NTP Server';
 
         case 'os-updates':
             return 'OS Updates';