Avoid to re-create groups if they already exists (bugs #3240)
Merge commit 'refs/changes/21/421/1' of http://gerrit.tuleap.net/tuleap into stable

* http://gerrit.tuleap.net/tuleap:
  Avoid to re-create groups if they already exists (bugs #3240)
This is Tuleap 5.12.99.69