Bug 12079: ensure that CheckReserves() includes reserve_id in its response

Bug 12079: ensure that CheckReserves() includes reserve_id in its response

This patch modifies _Findgroupreserve so that its one caller,
CheckReserves(), would include the reserve_id field in the
hold request it returns.

Failure to include reserve_id in every circumstance resulted
in bug 11947.  This patch is therefore a complementary fix for
that bug, but is not meant to preempt the direct fix for
that bug.

To test:

[1] Verify that t/db_dependent/Reserves.t passes.
[2] Verify that the following test plan taken from
    the patch for bug 11947 works for this patch
    *without* applying the patch for 11947:

* have a few borrowers, say 4.
* have a biblio with a single item (you can scale this up, it should
  work just the same.)
* issue the item to borrower A
* have borrowers B, C, and D place a hold on the item
* return the item, acknowledge that it'll be put aside for B.
* view the holds on the item.

Without the patch:
* the hold priorities in the UI end up being "waiting, 2, 1" when they
  should be "waiting, 1, 2".
* in the database "reserves" table, they're really "0, 2, 3" when they
  should be "0, 1, 2".

With the patch:
* the hold priorities in the UI end up being "waiting, 1, 2"
* in the database, they're "0, 1, 2"

Signed-off-by: Galen Charlton <gmc@esilibrary.com>
Signed-off-by: Bernardo Gonzalez Kriegel <bgkriegel@gmail.com>
Work as described. No koha-qa errors. Test pass

Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>
(cherry picked from commit 695fdebdee802387f45505a1350120727d3e2f7f)
Signed-off-by: Fridolin Somers <fridolin.somers@biblibre.com>