Bug 18789: (QA follow-up) Use patron object in batch checkout template

Bug 18789: (QA follow-up) Use patron object in batch checkout template

1) Enable batch checkouts in system preferences and set it on for some
patron categories
2) Try to batch checkout for some patron with one of these categories
--> without patch the batch checkout page is even not shown
--> with patch batch checking out is working as expected

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>