CryptoOutputStream throws IOException on flush() if stream is closed

With Druid and Hadoop 2.7.3 I see that calls to flush() on a closed CryptoOutputStream throws IOException.

Although flushing closed stream is dodgy, the culprit is actually CryptoOutputStream, according to the java documentation it look actually authorised.

The OutputStream java doc (http://docs.oracle.com/javase/8/docs/api/java/io/OutputStream.html#flush()) shows that flush should behave like close(), which allows being called on a closed stream without exception (as opposed to write() and others which clearly says should throw an exception)