Bug 17657: Fix locations of item types images

Bug 17657: Fix locations of item types images

Koha::ItemType->image_location takes the interface in parameter or
default to OPAC.
From the item types admin page, we need to specify the intranet
interface to retrieve the correct image's url

Test plan:
Go on the item types admin page, see the source of the page and find the
image' urls.
=> Without this patch, they point to the OPAC
=> With this patch, the location is correct

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Mason James <mtj@kohaaloha.com>