nfs: update documentation and example

[prksu]

Signed-off-by: Ahmad Nurus S prksu.sh@gmail.com
(cherry picked from commit c22189b)

Description of your changes:
We need to backport PR #6440 to release-1.4 as well

Which issue is resolved by this Pull Request:
Resolves #

Checklist:

• Commit Message Formatting: Commit titles and messages follow guidelines in the developer guide.
• Skip Tests for Docs: Add the flag for skipping the build if this is only a documentation change. See here for the flag.
• Skip Unrelated Tests: Add a flag to run tests for a specific storage provider. See test options.
• Reviewed the developer guide on Submitting a Pull Request
• Documentation has been updated, if necessary.
• Unit tests have been added, if necessary.
• Integration tests have been added, if necessary.
• Pending release notes updated with breaking and/or notable changes, if necessary.
• Upgrade from previous release is tested and upgrade user guide is updated, if necessary.
• Code generation (make codegen) has been run to update object specifications, if necessary.

[skip ci]