request #5979: Global notif is not sent if only field change

Expected behavior: notification is sent to global email if:
- there is a comment
- there is at least one field change the user can read (or we don't
  check perms)
- both

Change-Id: I1fb9ae916831432c7cab6dcbf794bde9c2d152d9
Merge commit 'refs/changes/42/1742/2' of ssh://gerrit.tuleap.net:29418/tuleap into HEAD

* ssh://gerrit.tuleap.net:29418/tuleap:
  request #5979: Global notif is not sent if only field change

Change-Id: Icda9385f76bb4c17bd40e3b7e0cbb7c15af22896
This is Tuleap 6.9.99.43

Change-Id: Ibc9e6bf2c6f55eabacb3ea902825e8ffab6f4b07