story #7508: Display a new pane in lab mode only

Change-Id: If3930fe543dd7b26cff70c5ab93e5d818d05b6bb
Merge commit 'refs/changes/37/3137/2' of ssh://gerrit.tuleap.net:29418/tuleap into HEAD

* ssh://gerrit.tuleap.net:29418/tuleap:
  story #7508: Display a new pane in lab mode only

Change-Id: I1a0191793ad8fef5132caeade5457f1528132e18
This is Tuleap 7.6.99.6

Change-Id: Ib72d4a9112b805ce76faced07b90d3e88636e38f