Show RRs from inactive users on "All Review Requests" and their user page.

Long ago we made a change that hid review requests from inactive users from the
dashboard. Unfortunately, this went way too far, hiding them from all
datagrids, including "All Review Requests" and their user page. As funny as it
is to "disappear" someone when they leave the company, it does make it harder
for people who are trying to find old changes.

Testing done:
* Set a user who had a couple old review requests as inactive. Saw that I could
  now see their changes in /r/ and /users/<user>/. Verified that their pending
  changes were still hidden from my dashboard.
* Ran unit tests.

Fixes bug 1436.

Reviewed at https://reviews.reviewboard.org/r/5488/