examples/stroage: use &bytes.Buffer{}
examples/stroage: use &bytes.Buffer{}

bytes.NewBuffer(nil) is not as nice.

Change-Id: Ief404f3dc4a655fe1e4dea8fbe5be940acaca671
Reviewed-on: https://code-review.googlesource.com/4781
Reviewed-by: Dave Day <4cba7a21e1f1fc896442779dcb55aeda6df97dfe@golang.org>

googleapis/google-cloud-go,googleapis/google-cloud-go,michael-grosshans/google-cloud-go,michael-grosshans/google-cloud-go,googleapis/google-cloud-go,googleapis/google-cloud-go