Fix ModifyLimitQueryTest

The functional <code>ModifyLimitQueryTest</code> makes false expectations about the query results. <code>LIMIT</code> queries without <code>ORDER BY</code> clause return non-deterministic results, therefore the test cannot make any expectations about which values are returned and in which order. You can only expect a certain number of results.
The test might still work on platforms like mysql when you assume results to be in an ascending order, because the database might put the results of a non-deterministic query in an ascending order by default. Still this is not reliable and not all vendors do that.
This PR changes the tests to have an ordered, deterministic results by default to have more reliable expectations. Also one test about a non-deterministic query was added, which just asserts the number of results returned.