Fixing compilation errors caused by Payload no longer being an InputSupplier

See JCLOUDS-622 and https://github.com/jclouds/jclouds/commit/80a0256c
Does this stream need to be closed in a `finally`? The Guava doc explicitly states that [toByteArray](http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/io/ByteStreams.html#toByteArray\(java.io.InputStream\)) will **not** close the stream.