S3 helper for changing the S3 Canned ACL of an existing object.

s3.setObjectAcl(path, cannedAcl, callback)

• 'path' - the S3 Path.
• 'cannedAcl' - the S3 Canned ACL.
• 'callback' - the callback that is executed when the processing finishes. It has a couple of arguments: error and result.
• If there's an error, the callback receives the error argument as Error instance.
• If the error argument is null, then the response argument contains the response.headers object as returned by the node.js core HTTPS client.