Fix request #6435 - Mandatory field in workflow doesn't enforce Text fields

Change-Id: I4d87ca6fc150bb5b12e19cfdc7727a400497cdb0
Merge commit 'refs/changes/81/2081/1' of ssh://gerrit.tuleap.net:29418/tuleap into stable

* ssh://gerrit.tuleap.net:29418/tuleap:
  Fix request #6435 - Mandatory field in workflow doesn't enforce Text fields

Change-Id: I720b4159cc5d2410ec04c87a130179501f88f93b
This is Tuleap 6.11.99.9

Change-Id: If16c0e5f7db88d785b1e9e7296b81ba18c5e75ad