Fix some bad attribute names for file attachment unit tests.
Review Request #10480 — Created March 31, 2019 and submitted
Some of our file attachment tests were setting the wrong attributes when
trying to create instances. These didn't really impact Django 1.6 at
all, but broke on Django 1.11. We didn't notice because we weren't
carefully checking the actual results in the only place we tried
looking, the API tests.
This updates those tests to set the correct attribute names and to be
more explicitly check what's set in any API payloads.
Unit tests pass on Django 1.6 and 1.11 (in combination with other