Reordered transaction rollback to be called before an error is raised.

Review Request #9494 — Created Jan. 19, 2018 and submitted — Latest diff uploaded

Information

Review Board
release-4.0.x
d6445c2...

Reviewers

The loaddb management command had a bug where the code to rollback the
transaction occured after a "raise", meaning it would never be reached.
I reordered this so the raise happens after the transaction code.

There aren't a ton of tests in the reviewboard/admin module but the 5 tests in there ran successfully.