This is a fix for the bug I introduced in the fix to 3465.
With this fix:

 - Change descriptions are no longer published on initial review request publishings.

 - Discarding no longer modifies the fields in the change description (aside from status, which it always did) 
The refactored code pretty much changes the state prior to the shipped fix of 3465, and extracts the "copying over from draft to review request" part to a separate function. That function is then called if a private unpublished review request is discarded.

Ran existing unit tests & passed
Modified previous unit tests that I wrote to reflect the "copying over" part and not the change description. Passed.
Added a test to make sure change descriptions are no longer published on initial review request publishings.
Also manual tests of the above!