Fix the method calls of QueryTest.checkAnswer

Currently, the method `checkAnswer` in Object `QueryTest` returns an optional string. It doesn't throw exceptions when errors happen.
The actual exceptions are thrown in the trait `QueryTest`.

However, there are some test suites that use the no-op method `QueryTest.checkAnswer` and expect it to fail test cases when the input Dataframe doesn't match the expected answer. E.g. StreamSuite, SessionStateSuite, BinaryFileFormatSuite, etc.

We should fix this.