Fix #1705 : MySQL connection might be lost after long operations

lib/classes/patch/370alpha7a.php

@@ -65,6 +65,7 @@ class patch_370alpha7a implements patchInterface
             $stmt = $conn->prepare($sql);
             $stmt->execute();
             $rs = $stmt->fetchAll();
+            $stmt->closeCursor();
         } catch (\PDOException $e) {
             // table not found
             if ($e->getCode() == '42S02') {

lib/classes/patch/370alpha8a.php

@@ -72,8 +72,8 @@ class patch_370alpha8a implements patchInterface
         if (($stmt = $conn->prepare($sql)) !== FALSE) {
             $stmt->execute();
             $ttasks = $row = $stmt->fetchAll();
-            $stmt->closeCursor();
         }
+        $stmt->closeCursor();
 
         $tdom = array();     // key = period
         $taskstodel = array();