Change to use list_next api to get all artifacts for a given build

BUG=b:62141068
TEST=local devserver test

Change-Id: I758a190c72bcff3832119958ce66dce55678617f
Reviewed-on: https://chromium-review.googlesource.com/522889
Commit-Ready: Kris Rambish <krisr@chromium.org>
Tested-by: Dan Shi <dshi@google.com>
Reviewed-by: Kris Rambish <krisr@chromium.org>
1 file changed