v3: resp.Body is not closed in s3.PutReaderWithHeader

[vitaliel]

http://golang.org/pkg/net/http/#Client.Do
Callers should close resp.Body when done reading from it. If resp.Body is not closed, the Client's underlying RoundTripper (typically Transport) may not be able to re-use a persistent TCP connection to the server for a subsequent "keep-alive" request.

We encountered stale sockets for the process and at the end it fails with too many open files. It happens with s3-eu-west-1.amazonaws.com backend.

go version 1.3

[axw]

@vitaliel Thanks for the report.