Hadoop Filesystem silently fails

Hi,

beam Filesystem operations copy, rename and delete are void in SDK. Hadoop native filesystem operations are not and returns void. Current implementation in Beam ignores the result and pass as long as exception is not thrown.

I got burned by this when using 'rename' to do a 'move' operation on HDFS. If target directory does not exists, operations returns false and do not touch the file.

https://github.com/apache/beam/blob/master/sdks/java/io/hadoop-file-system/src/main/java/org/apache/beam/sdk/io/hdfs/HadoopFileSystem.java#L148