message: ci: save space during docker push
  This is yet another workaround for lack of disk space but should allow
  us to limp around for a while longer.
diff: @@ -15,15 +15,14 @@ do
  done
  if [ "$TRAVIS_PULL_REQUEST" == "false" ] && [ "$want_push" == "true" ]
  then
  - # this is needed to verify the example images
  docker build -f ci/Dockerfile-envoy-image -t lyft/envoy:latest .
  - # verify the Alpine build even when we're not pushing it
  - make -C ci/build_alpine_container
  -
  docker login -u $DOCKERHUB_USERNAME -p $DOCKERHUB_PASSWORD
  docker push lyft/envoy:latest
  docker tag lyft/envoy:latest lyft/envoy:$TRAVIS_COMMIT
  docker push lyft/envoy:$TRAVIS_COMMIT
  + docker rmi $(docker images -a -q)
  +
  + make -C ci/build_alpine_container
  docker tag lyft/envoy-alpine:latest lyft/envoy-alpine:$TRAVIS_COMMIT
  docker push lyft/envoy-alpine:$TRAVIS_COMMIT
  docker push lyft/envoy-alpine:latest
  