For use with (threaded?) expanders.
Filters for tasks without plan elements.
This allows tasks which may be the child of another task
(e.g., DetermineRequirement tasks that are child of GLS)
(unlike UTILExpandableTaskCallback which also filters tasks with no workflow)
getPredicate() overridden to ignore workflow
Just calls plugin interestingTask method.
BUG FIX (deployment date perturbation bug) :
Does NOT skip tasks that already have a plan element - this
will be true on rehydration.