Fix "Cannot move project" error message from popping up after a successful transfer

The JavaScript click handlers were never being removed, leading to duplicate requests when attempting to transfer a project to another namespace. The first transfer would succeed but the subsequent ones would fail, leading to the error message saying, "Cannot move project".

![image](https://gitlab.com/stanhu/gitlab-ce/uploads/0c9f61294291514e0c2a48c204b6a1aa/image.png)

I attempted to write a unit test for this, but it was taking me too long to get it right.

Closes #1448 and #1128

See merge request !548