Fix S3 abortable stream warning

[greglook]

The S3 client has an annoying tendency to log lots of warnings when not all bytes are read from an input stream before it is closed. It does this because S3 is already sending the rest of the data, so the connection must be aborted and cannot be reused in a connection pool. Sometimes this is legitimately a performance hit, but other times consuming the remainder of a multi-megabyte stream is going to me more expensive than re-establishing a connection.

This library should take a page from Hadoop and wrap the S3 input stream with additional closing logic. See the following for references:

• https://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/services/s3/internal/S3AbortableInputStream.html
• https://issues.apache.org/jira/browse/HADOOP-14596

[greglook]

Fixed by always draining the input stream in 0cc8710.