Bug 10423: Show date due with time if it's a hourly loan

Bug 10423: Show date due with time if it's a hourly loan

On printing the summary from the patron account, the hours are not
displayed if needed.
The as_date_due flag should be set to display it correctly.
Problem, GetPendingIssues modify the value retrieved from the database.
In order to not add regression and check all calls to GetPendingIssues,
this patch backup the value before the change.

Test plan:
Check some items out, specify a hourly loan for some.
Click on print > print summary and confirm the date due are correctly
formatted.

Followed test plan. Date + time display as expected.
Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>