[#714] Fix an intermittently failing test

This test depends on the order of the two datasets. The default sort
order has changed now to most-recently-modified-first when there's no
search query, and since the test creates the two datasets in a random
order the search returns the datasets in a different order each time the
test is run, giving a 50/50 chance that the test will fail.

Change the test to not depend on the fixed order of the datasets.