Bug 20144: [sql_modes] Do not store 0000-00-00

Bug 20144: [sql_modes] Do not store 0000-00-00

This patch needs to be linked with bug 20145.

Fix for:
Incorrect date value: '0000-00-00' for column 'dateexpiry'

We cannot longer store 0000-00-00, but no need to.
The tests must be kept for now as long as bug 20145 has a solution

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>