Added failing test for issue #5025.

[workmanw]

Ping @stefanpenner -- As promised, a failing test.

One thing to note is this assertion:

    assert.equal(get(people, 'length'), 2, 'Unloaded record removed from the array');

This would technically have failed before the previous regression because instead of nullifying the record in the list, it just left the stale value until the end of the loop. If the goal is to restore that behavior, then we need to change the test criteria.

And I would be happy to do that, let me know.

---

For reference a test of the previous functionality would look like:

run(() => {
  people.objectAt(0).unloadRecord();
  
  assert.equal(get(people, 'length'), 3, 'Unload does not complete until the end of the loop');
  assert.ok(get(people.objectAt(0), 'name'), 'Scumbag Dale', 'Dale is still the first object until the end of the loop');
});

assert.equal(get(people, 'length'), 2, 'Unloaded record removed from the array');
assert.ok(get(people.objectAt(0), 'name'), 'Scumbag Katz', 'Katz shifted down after the unload');
assert.ok(get(people.objectAt(1), 'name'), 'Scumbag Bryn', 'Bryn shifted down after the unload');

[runspired]

I ported this test into #5378 and confirmed that the fix for #5350 also fixes this issue.