[FLINK-2268] Don't use commons-io ByteArrayOutputStream in NFATest

commons-io is only usable as a transitive dependency of the Hadoop
dependencies. We can just use the Java ByteArrayOutputStream and
get rid of that dependency.

flink-libraries/flink-cep/src/test/java/org/apache/flink/cep/nfa/NFATest.java

@@ -29,10 +29,10 @@ import org.apache.flink.core.memory.DataOutputViewStreamWrapper;
 import org.apache.flink.streaming.runtime.streamrecord.StreamRecord;
 import org.apache.flink.util.TestLogger;
 
-import org.apache.commons.io.output.ByteArrayOutputStream;
 import org.junit.Test;
 
 import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
 import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collection;