Fix request #6286: Fatal error when importing a tracker with cardwall semantics to a server w/o cardwall enabled

Change-Id: I73bf3af25ef5361dcc3e60577baf30cb099c98f7
Merge commit 'refs/changes/67/1967/1' of ssh://gerrit.tuleap.net:29418/tuleap into tuleap-stable-master

* ssh://gerrit.tuleap.net:29418/tuleap:
  Fix request #6286: Fatal error when importing a tracker with cardwall semantics to a server w/o cardwall enabled

Change-Id: I1c3ab093269fba21686784087ed87e225a253872
Tuleap 6.10.99.36

Change-Id: I4cfc675d1fb5369ac82d655a1108dd2c04a8659c