Bug 15445 DateUtils.t fails on Jenkins due to server sluggishness

 Bug 15445 DateUtils.t fails on Jenkins due to server sluggishness

Jenkins server is abnormally slow to perform a task done in less than
1s elsewhere. The test stay valid by giving just a bit more time to Jenkins
server.

TO TEST:
- Confirm that the two test hasn't changed. They the just get 4s to
  perform
- Push the patch to master and observe that DateUtils.t doesn't fail
  anymore.

NOTE: Also passed koha qa test tools too.

Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Amended: Changed to 2s, should be enough

Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>