[DATABASE] Update "modified" in Managed_DataObject instead of a DBMS trigger

Instead of relying on the MariaDB's ON UPDATE CURRENT_TIMESTAMP trigger update
"modified" attributes in Managed_DataObject. Every raw query that needs
adjusting is adjusted, as they won't update "modified" automatically anymore.

The main goal behind this change is to fix "modified" updates on PostgreSQL.

classes/File_redirection.php

@@ -468,7 +468,7 @@ class File_redirection extends Managed_DataObject
                 throw new ServerException('Unknown DB type selected.');
         }
         $tablefix->query(sprintf(
-            'UPDATE %1$s SET urlhash = %2$s;',
+            'UPDATE %1$s SET urlhash = %2$s, modified = CURRENT_TIMESTAMP;',
             $tablefix->escapedTableName(),
             $url_sha256
         ));