Update script update.sh should exit non-zero when fetching tarball failed #1269

~/docker-node $ ./update.sh 14
Updating version 14...
14/stretch-slim/Dockerfile is already up to date!
14/buster/Dockerfile is already up to date!
14/buster-slim/Dockerfile is already up to date!
14/stretch/Dockerfile is already up to date!
curl: (22) The requested URL returned error: 404 Not Found
14/alpine3.10/Dockerfile is already up to date!
curl: (22) The requested URL returned error: 404 Not Found
14/alpine3.11/Dockerfile is already up to date!
Done!