Add some Abortable.abort() interface for streams etc which can be terminated

Some IO we want to be able to abort rather than close cleanly, especially if the inner stream is an HTTP connection which itself supports some abort() method. For example: uploads to an object where we want to cancel the upload without close() making an incomplete write visible.

Proposed: Add a generic interface which things like streams can implement

AbortableIO {
  public void abortIO() throws IOE;
}

+do for s3a output stream. I wouldn't do this a passthrough on FSDataOutputStream because we need to consider what expectations callers have of an operation being "aborted"