request #7345: Tv3 export to Tv5: import failure when field name is not unique

Assume that we only import for used fields

Change-Id: Ie0685dfd4eacb9674d9ad19a27abfc6d19833e84
Merge commit 'refs/changes/95/2895/1' of ssh://gerrit.tuleap.net:29418/tuleap into HEAD

* ssh://gerrit.tuleap.net:29418/tuleap:
  request #7345: Tv3 export to Tv5: import failure when field name is not unique

Change-Id: I4aeaa790d87cf4d8a576d39d32e1f53c4aa50938
This is Tuleap 7.3.99.56

Change-Id: I6c114bcbe9c0ad446b3319aeff622fc24e117421