When publishing a Review, we let the ReviewRequest compute its own

last updated time, which ends up being mere milliseconds after

Review.timestamp, which makes it always appear that the review request

is always the last updated object returned by

ReviewRequest.get_last_activity(). The same is true for DiffSets

during publishing of review requests -- their timestamp is always

behind.
We now force the timestamp of ReviewRequest to be in sync with

Review.timestamp when publishing a review and DiffSet.timestamp when

publishing a review request that contains a new diff. With in-sync

timestamps, ReviewRequest.get_last_activity() now returns the correct

models.
Co-authored-by: Anni Cao anni@sfu.ca.

Ran unit tests.
Built the docs and went through them.
Manually verified the following before applying the patch

(via ./reviewboard/manage.py shell):

ReviewRequest.get_last_activity() returns the review request

  after a review is published.
ReviewRequest.get_last_activity() returns the review request

  after a revision with a diffset is published.

After applying the patch this is no longer the case.