Bug 17603: Remove itemtype-related Borrower_Discharge.t warnings

Bug 17603: Remove itemtype-related Borrower_Discharge.t warnings

This patch makes t/db_dependent/Patron/Borrower_Discharge.t create
good sample data for its tests. It does so by creating a random
itemtype.

To test:
- Run
  $ prove t/db_dependent/Patron/Borrower_Discharge.t
=> FAIL: lots of warnings about "item-level_itypes set but no itemtype
set for item"
- Apply the patch
- Run:
  $ prove t/db_dependent/Patron/Borrower_Discharge.t
=> SUCCESS: Tests are green, and no warnings.
- Sign off :-D

Sponsored-by: ByWater Solutions
Signed-off-by: Hector Castro <hector.hecaxmmx@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>