Bug 9788: (follow-up) Unit tests for changed routine GetReservesFromItemnumber

Bug 9788: (follow-up) Unit tests for changed routine GetReservesFromItemnumber

Adds three tests to Reserves.t for GetReservesFromItemnumber.
We test if this routine does not return a future next available hold,
a future item level hold. And if it does return a future wait (that is:
a confirmed future hold, using ConfirmFutureHolds).

Note that Holds.t does also contains some basic tests for this routine,
but the additional tests seem to better located in the direct context of
tests for bug 9761 for ConfirmFutureHolds.

Test plan:
Run both t/db_dependent/Holds.t and t/db_dependent/Reserves.t.
Verify if both tests do not fail.

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@biblibre.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit d211fa50ede180ed511cdf7f55be6c084abc1ff5)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>