Add sort control to hostgroup summary and fix sort rules for the generic group summary

refs #4185

modules/monitoring/application/views/scripts/list/hostgroups.phtml

@@ -1,4 +1,5 @@
 <div data-icinga-component="app/mainDetailGrid">
+    <?= $this->sortControl->render($this); ?>
     <?= $this->paginationControl($hostgroups, null, null, array('preserve' => $this->preserve)); ?>
     <table class="table table-condensed">
         <tbody>

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

@@ -35,10 +35,14 @@ class Groupsummary extends DataView
 
     public function getSortRules()
     {
+        if (in_array('servicegroup_name', $this->getQuery()->getColumns())) {
             return array(
                 'servicegroup_name' => array(
                     'order' => self::SORT_ASC
-            ),
+                )
+            );
+        }
+        return array(
             'hostgroup_name' => array(
                 'order' => self::SORT_ASC
             )