storage/gcsupload: don't close client and return handles (#319)
storage/gcsupload: don't close client and return handles (#319)

Handles aren't valid once the client is closed.

See: https://code-review.googlesource.com/16950
GoogleCloudPlatform/golang-samples,adamyanliev/golang-samples,GoogleCloudPlatform/golang-samples,GoogleCloudPlatform/golang-samples,adamyanliev/golang-samples,adamyanliev/golang-samples,adamyanliev/golang-samples