State summaries: Don't sort by default

Sorting the summaries (by host or service name) makes no sense and
even fails for PostgreSQL as it would require adding the column to
the GROUP BY clause.

library/Icingadb/Model/HoststateSummary.php

@@ -66,4 +66,9 @@ class HoststateSummary extends Host
             ]
         );
     }
+
+    public function getDefaultSort()
+    {
+        return null;
+    }
 }

library/Icingadb/Model/ServicestateSummary.php

@@ -71,4 +71,9 @@ class ServicestateSummary extends Service
             ]
         );
     }
+
+    public function getDefaultSort()
+    {
+        return null;
+    }
 }