Update the 'createDisuss' helper to be appended to the DOM using 'dom.prepend' to
benefit of its 'on_(attach|detach)_callback' calls. This allows the mail test suite
environment to be closer to the actual action behaviour (having those methods called
each time it is created/destroyed).
Some tests in which these methods were manually called have been adapted.
Also, one of the tests was destroying the action too quickly and exposed an issue
within the Discuss action, in the 'on_detach_callback' method. It has thus been
fixed as well.
Julien Mougenot
c9ce8a07e1