cmd/release: update to new storage API
cmd/release: update to new storage API

Change-Id: I6c06f00a2fc85852257d72c45656462b5e5e41d2
Reviewed-on: https://go-review.googlesource.com/17392
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/build,proppy/build,proppy/build,golang/build,golang/build,proppy/build,golang/build,proppy/build