SlaReport: Disconnect from the database when done

This hook usually runs isolated and no-one else requires a connection.
Makes only a difference in case of reporting triggering this as part
of a scheduled report and prevents the database connection from being
left open unnecessarily and failing upon re-use.

(cherry picked from commit e56d8a68ca)

library/Icingadb/ProvidedHook/Reporting/SlaReport.php

@@ -127,6 +127,11 @@ abstract class SlaReport extends ReportHook
 
         $rd->setRows($rows);
 
+        // Disconnect from the database, as this hook usually runs isolated and no-one else requires a connection.
+        // Makes only a difference in case of reporting triggering this as part of a scheduled report and prevents
+        // the database connection from being left open unnecessarily and failing upon re-use.
+        $this->getDb()->disconnect();
+
         return $rd;
     }