fix tests in ArtifactXMLExporterTestPHP53 (user->users)

Change-Id: I89608cc6ed4f35dd193c27a36ba87315591ee538
Merge commit 'refs/changes/97/2497/1' of ssh://gerrit.tuleap.net:29418/tuleap into HEAD

* ssh://gerrit.tuleap.net:29418/tuleap:
  fix tests in ArtifactXMLExporterTestPHP53 (user->users)

Change-Id: I9d3bf59f9b48a9a4a054807bc79481bb1396b6e6
This is Tuleap 7.0.99.48

Change-Id: I55011747c09073e899ef1f910558fb6446b72603