Documentation: Fix sysfs path for the NFSv4 client identifier

The sysfs path for the NFS4 client identfier should start with
the path component of 'nfs' for the kset, and then the 'net'
path component for the netns object, followed by the
'nfs_client' path component for the NFS client kobject,
and ending with 'identifier' for the netns_client_id
kobj_attribute.

Fixes: a28faadd ("Documentation: Add an explanation of NFSv4 client identifiers")
Link: https://bugzilla.redhat.com/show_bug.cgi?id=1801326


Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>