getReaderSize() returns wrong size for non regular files

[xxorde]

The function getReaderSize(reader io.Reader) (size int64, err error) from api-put-object.go returns the wrong size for non regular files on linux systems.

The problem can be demonstrated with pipes.

cmd := exec.Command("uptime")
stdout, err := cmd.StdoutPipe()
...
n, err := minioClient.PutObject(bucket, filename, stdout, "")

A full demonstration can be found here: https://github.com/xxorde/minio-go-bug

An ugly hotfix can be found here: xxorde@a0e2ffa

Thanks to @harshavardhana and @vadmeste for discussing the problem (https://gitter.im/minio/minio).

[harshavardhana]

Fixed by #551