request #7239 - LDAP/Tuleap user synchronization no longer retrieve extra attributes

Regression introduced by request #7151 (commit feb42fe)

Before that modification, Tuleap retrieved all LDAP default attributed.
After this patch, if a site use a custom LDAP_UserSync (in
/etc/tuleap/plugins/ldap/site-content/synchronize_user.txt) and rely on extra
paramters for custom synchronization, the process will be broken.

This commit rewrite (with test) the LDAP authentication and ensure that extra
params are fetched if they are defined.

Change-Id: I28ff80b102de9fe1e6be1f79f1583c7f580cfa6b
Merge commit 'refs/changes/87/2787/3' of ssh://gerrit.tuleap.net:29418/tuleap into tuleap-stable-master

* ssh://gerrit.tuleap.net:29418/tuleap:
  request #7239 - LDAP/Tuleap user synchronization no longer retrieve extra attributes

Change-Id: I3a79682daacc0f13b2e2cb5718a61392c62cdaed
Tuleap 7.3.99.32

Change-Id: Iaa0956e73c03d20f1c4385802d700db00cf20003