DataView\Contactgroup: Do not permit querying case-insensitive columns

refs #8163

modules/monitoring/library/Monitoring/DataView/Contactgroup.php

@@ -17,13 +17,9 @@ class Contactgroup extends DataView
     public function getColumns()
     {
         return array(
-            'contact',
             'contact_name',
-            'contactgroup',
             'contactgroup_name',
             'contactgroup_alias',
-            'host',
-            'service'
         );
     }
 
@@ -43,4 +39,9 @@ class Contactgroup extends DataView
             )
         );
     }
+
+    public function getFilterColumns()
+    {
+        return array('contactgroup', 'contact', 'host', 'service');
+    }
 }