Fix ChangeTagsTest failing on Postgres

Fix ChangeTagsTest failing on Postgres

The order of elements returned by the SELECT is not guaranteed. But the
assertEquals() can't know this. It does not know how to identify the two
objects, other than by their array index.

Using assertArrayEquals() would fix this. But I honestly don't like this
helper method. It is expensive, for example. So I went for an ORDER BY.

An example for this failure can be seen here:
https://integration.wikimedia.org/ci/job/mediawiki-quibble-vendor-postgres-php70-docker/2484/console

Change-Id: I284d13d21b9bc34270307e78430180d94fc6665e