Setting NUFA does not work

[jakkul]

https://github.com/gluster/glusterdocs/blob/main/docs/Administrator-Guide/Managing-Volumes.md

Use the following command to enable NUFA:

# gluster volume set <VOLNAME> cluster.nufa enable

^^^^^ This does not work.

What one must do is to:

• create a group or pick a settings group that you'll use to manage settings of a particular volume
• define cluster.nufa enable for this group:

# echo "cluster.nufa=on" | tee -a /var/lib/glusterd/groups/<GROUPNAME>

• add your volume to the group

# gluster volume set <VOLNAME> group <GROUPNAME>

• verify if the nufa setting worked

# gluster volume info

[jakkul]

I've made a pull request with a proposed documentation fix.