Bug 20144: [sql_modes] Fix date format in tests

Bug 20144: [sql_modes] Fix date format in tests

Fix for:
Incorrect date value: '01-01-2013' for column 'startdate'
Incorrect date value: '01-01-2016' for column 'budget_period_enddate'
Incorrect date value: '30-11-2013' for column 'enddate'
Incorrect date value: '31-12-2015' for column 'budget_period_enddate'
Incorrect date value: '12-31-2015' for column 'budget_period_enddate'
Incorrect date value: '01-01-2014' for column 'entrydate'

Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Julian Maurice <julian.maurice@biblibre.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>