CORE-617 Save and Add Another is duplicating tasks

I've tracked the issue item duplication issue down to how `"{original_list} add"` and `"{original_list} remove"` are implemented. These two functions seem to be executing multiple times when you open the modal and even more times when you save. These seems to cause a race condition when you open a new modal immediately after saving, and this seems to cause the newly added item to be pushed into the DOM twice.

I noticed that increasing the timeout seems to fix the issue of duplication, but this code should really be revised soon.