Bug 13172 t/Koha_Email.t was database dependent

Bug 13172 t/Koha_Email.t was database dependent

To test
1/ Stop your database server
2/ run t/Koha_Email.t
3/ Notice the errors
4/ Apply patch
5/ run t/Koha_Email.t again
6/ No errors

(Don't forget to restart your db server after)

Signed-off-by: Robin Sheat <robin@catalyst.net.nz>
Verified that it fixes a package build.

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
Works as described, tests pass now without database connection.

Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>