Bug 13459: Fix datatables paging for admin > itemtypes

Bug 13459: Fix datatables paging for admin > itemtypes

To test:
- Go to administration > itemtypes
- Verify the display of the paging options is broken
- Apply patch
- Verify the display is now correct and works nicely

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
(cherry picked from commit 225432a1f039a9c625e24e3c59643db331fe17b2)
Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>