There are 2 approaches to backing up NFS mounts, depending on your need.
If you want to back up specific NFS mounts, you can create subclients and list those paths explicitely. I recommend doing this in a separate backupset if you are using 1-Touch or may use it in the future. If you back up NFS mounts in the defaultBackupSet, 1-Touch will restore them to local disk during recovery.
The other alternative, if you want Commvault to not skip any NFS mounts, is to customize the list of skipped filesystems. This is done via the ignoreFSType additional setting. Configure this at the client level setting the value to the default shown, but remove ':nfs:'.