Current code does not print any response headers from httputil.DumpResponse().

   PUT /miniocloud/new-file HTTP/1.1
   Host: s3.amazonaws.com
   User-Agent: Go-http-client/1.1
   Content-Length: 11
   Accept-Encoding: gzip

   HTTP/1.1 200 OK

With this fix we get an appropriate output for httputil.DumpResponse().

   PUT /miniocloud/new-file HTTP/1.1
   Host: s3.amazonaws.com
   User-Agent: Go-http-client/1.1
   Content-Length: 11
   Accept-Encoding: gzip

   HTTP/1.1 200 OK
   Content-Length: 0
   Date: Thu, 14 Jan 2016 03:04:42 GMT
   Etag: "3e25960a79dbc69b674cd4ec67a72c62"
   Server: AmazonS3
   X-Amz-Id-2: qnXyH6sknlovV0Myy3emFAXTNtI/sQIcu1ZXNq/6wd17K32tQ7WNGB1qb3nzCpW2DhfeZ/MbWfw=
   X-Amz-Request-Id: 8422EACB0CC492BD

Fixes #13942

Change-Id: Ida063cc3524a96170d8a837893f7c9f49b6cf98e
Reviewed-on: https://go-review.googlesource.com/18624Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>