[SPARK-13584][SQL][TESTS] Make ContinuousQueryManagerSuite not output logs to the console

## What changes were proposed in this pull request?

Make ContinuousQueryManagerSuite not output logs to the console. The logs will still output to `unit-tests.log`.

I also updated `SQLListenerMemoryLeakSuite` to use `quietly` to avoid changing the log level which won't output logs to `unit-tests.log`.

## How was this patch tested?

Just check Jenkins output.

Author: Shixiong Zhu <shixiong@databricks.com>

Closes #11439 from zsxwing/quietly-ContinuousQueryManagerSuite.