* Backend - Starting the container build from scratch
This reduces the image size, reduces the attack surface and avoids security vulnerabilities.
Fixes https://github.com/kubeflow/pipelines/issues/1545
* Starting building other controller images from scratch
* add vendor to gitignore
* switch to go module
* switch to go module
* switch to go module
* prune go mod
* prune go mod
* turn on go mod for test
* enable go module in docker image
* enable go module in docker image
* fix images
* debug
* debug
* debug
* update image