Bug 24150: Prevent random failure comparing updated_on

Bug 24150: Prevent random failure comparing updated_on

Jenkins is currently failing (slow server, datetime comparison, etc.)

koha_1       |     #   Failed test at t/db_dependent/Koha/Old.t line 48.
koha_1       |     #     Structures begin differing at:
koha_1       |     #          $got->{updated_on} = '2020-01-07 14:15:22'
koha_1       |     #     $expected->{updated_on} = '2020-01-07 14:15:21'
koha_1       |     # Looks like you failed 1 test of 1.
koha_1       |
koha_1       | #   Failed test 'Koha::Old::Patrons'
koha_1       | #   at t/db_dependent/Koha/Old.t line 49.
koha_1       | # Looks like you failed 1 test of 2.
koha_1       | [14:15:22] t/db_dependent/Koha/Old.t ...............................................

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