[SPARK-21946][TEST] fix flaky test: "alter table: rename cached table" in InMemoryCatalogedDDLSuite

## What changes were proposed in this pull request?

This PR fixes flaky test `InMemoryCatalogedDDLSuite "alter table: rename cached table"`.
Since this test validates distributed DataFrame, the result should be checked by using `checkAnswer`. The original version used `df.collect().Seq` method that does not guaranty an order of each element of the result.

## How was this patch tested?

Use existing test case

Author: Kazuaki Ishizaki <ishizaki@jp.ibm.com>

Closes #19159 from kiszk/SPARK-21946.