Bug 16403: Fix holds.t (tests 9 and 39)

Bug 16403: Fix holds.t (tests 9 and 39)

Resolves this:

Failed test 'GetReservesFromItemnumber should return a valid borrowernumber'
at t/db_dependent/Holds.t line 97.
          got: '2000001890'
     expected: '2000001889'
Failed test 'Test AlterPriority(), move to bottom'
at t/db_dependent/Holds.t line 220.
          got: '4'
     expected: '5'

Test plan:
Run the test before and after applying this patch.

Signed-off-by: Marc Véron <veron@veron.ch>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>