Bug 9392: confirmation does not appear for negative notforloan items issues

When checking-out an item marked "not for loan" with a positive value,
you get a message to forbid or confirm issue (depending on
AllowNotForLoanOverride syspref).  For an item with a negative value
(usually during acquisition process), the issue is made without forbid
or confirm message.

This patch simply changes the test notforloan > 0 into notforloan != 0.

Test plan :
- Checkout an item with items.notforloan = 0
=> The item is issued without message
- Checkout an item with items.notforloan > 0
=> A message forbids or asks confirmation to override
- Checkout an item with items.notforloan < 0 (e.g., on order)
=> A message forbids or asks confirmation to override

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Checked with AllowNotForLoanOverride on and off.
All tests and QA script pass.
Signed-off-by: Jared Camins-Esakov <jcamins@cpbibliography.com>
Merge branch 'bug_9392' into 3.12-master