Bug 24590: Fix Koha/Object.t on MySQL 8

Bug 24590: Fix Koha/Object.t on MySQL 8

% prove t/db_dependent/Koha/Object.t
is failing on MySQL 8 with:

 kohadev-koha@9bbf9ac68519:/kohadevbox/koha$ prove t/db_dependent/Koha/Object.t
 t/db_dependent/Koha/Object.t .. 15/18
     #   Failed test 'Exception field is correct'
     #   at t/db_dependent/Koha/Object.t line 650.
     #          got: 'api_keys.secret'
     #     expected: 'secret'
     # Looks like you failed 1 test of 16.
 t/db_dependent/Koha/Object.t .. 16/18
 #   Failed test 'store() tests'
 #   at t/db_dependent/Koha/Object.t line 723.

MySQL 8 displays the tablename in the error.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>