Fix NFS issues for Mac version Catalina and up
Mac native NFS setup script is broken from Mac version Catalina and up. It is due to the change in the volume directory path.
This PR is backward compatible. All versions before Catalina will be using ``/Users`` and from Catalina ``/System/Volumes/Data`` will be used.
There was an attempt to fix that issue via https://github.com/edx/devstack/pull/521. But that PR seems to be closed without merging.
1. Pull this PR in a Mac Catalina or Big Sur
2. Try to setup NFS. It should work.
3. Setting up NFS should work across all versions of Mac.