HadoopSeekableByteChannel breaks when backing InputStream doesn't supporte ByteBuffers

This happened last summer, when I wanted to use S3A as the backing HDFS access implementation. 

This is because while this method is called : https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FSDataInputStream.java#L145

This class does not implement ByteBuffer readable https://github.com/apache/hadoop/blob/trunk/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java

I fixed it by manually incrementing the read position and copying the backing array instead of buffering.

https://github.com/Igosuki/beam/commit/3838f0db43b6422833a045d1f097f6d7643219f1

I know the s3 direct implementation is the preferred path, but this is possible, and likely happens to a lot of developers.