request #3468 and request #3467 - Centos6 install compatibility

request #3468 - [CentOS 6] SELinux forbids apache to send emails
request #3467 - [CentOS6] error setting SELinux context in setup.sh

Thanks to Dominique Leducq and Nicolas Pascal for proposing the up-to-date
values.

Change-Id: Icbbfd3506d2dbc8c98864482fe9529efae3929f5
Merge commit 'refs/changes/18/1518/2' of ssh://gerrit.tuleap.net:29418/tuleap into HEAD

* ssh://gerrit.tuleap.net:29418/tuleap:
  request #3468 and request #3467 - Centos6 install compatibility

Change-Id: Ia12a56d2e73555cf1f27b994a06671a40f1ecc91
This is Tuleap 6.7.99.29

Change-Id: I14f44e64e881c63c2b31874c438e63c8583cc9fe