[tests] Add TestLogger to StreamCheckpointNotifierITCase

Saw this one failing, but it's impossible to get any insight
from the logs, because you can't tell what is what.

flink-tests/src/test/java/org/apache/flink/test/checkpointing/StreamCheckpointNotifierITCase.java

@@ -37,6 +37,7 @@ import org.apache.flink.streaming.api.operators.TwoInputStreamOperator;
 import org.apache.flink.test.util.ForkableFlinkMiniCluster;
 import org.apache.flink.util.Collector;
 
+import org.apache.flink.util.TestLogger;
 import org.junit.AfterClass;
 import org.junit.BeforeClass;
 import org.junit.Test;
@@ -70,7 +71,7 @@ import static org.junit.Assert.fail;
  * successfully completed checkpoint.
  */
 @SuppressWarnings("serial")
-public class StreamCheckpointNotifierITCase {
+public class StreamCheckpointNotifierITCase extends TestLogger {
 	
 	private static final int NUM_TASK_MANAGERS = 2;
 	private static final int NUM_TASK_SLOTS = 3;