LINSTOR CSI builder

Build + package linstor-csi in a Docker image.

Create a new release

1. ./linstor-csi to point to the new upstream commit.
2. edit ./Dockerfile to use the new release version as default for ARG SEMVER. There is a make target to do that for you:

   make prepare-release SEMVER=<version>
   
3. Add changelog entries here and here.
4. git commit + git tag
5. push master + tag to gitlab