NFS server container for testing
This container exports '/' directory with an index.html inside. NFSv4 only.
Accepts a -G option for specifying a group id to give exported directories. Clients in the specified group will have full rwx permissions, others none.
Inspired by https://github.com/cpuguy83/docker-nfs-server.
Used by test/e2e/* to test NFSVolumeSource. Not for production use!
