Bug 10305 - _increment_barcode is called twice

Bug 10305 - _increment_barcode is called twice

For some reason, _increment_barcode is called twice in succession in
cataloguing/additem.pl

Test Plan:
1) Enable autobarcode = incremental
2) Catalog an item, not the barcode
3) Apply this patch
4) Catalog another item, the barcode should be the next in line
   as previously. No change should be noted.

Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
(cherry picked from commit 449fc4e168368cc3b1991152f32a2862b578a04c)
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>