Comment 2 for bug 1612752

Branch here: http://git.evergreen-ils.org/?p=working/Evergreen.git;a=shortlog;h=refs/heads/user/csharp/lp1612752_transit_cancel_improvements

It works on current master as far as I am able to tell - I would appreciate testing and code review.

In my second (top) commit, I changed the end-user-facing "abort" term to "cancel". I'm open to changes for that too.