Bug 14598 [QA Followup] - Correct the behavior of GetItem

Bug 14598 [QA Followup] - Correct the behavior of GetItem

Currently GetItem sets itemtype to the biblio itemtype if no item level
itemtype exists. Instead, it should only do this if item_level-itypes
is not set.

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
(cherry picked from commit 73b85e98755e075044db72b973cb3ebd6c0f4891)
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>