nfsv3: fix hard link creation (similar to http://rb.dcache.org/r/6224)

    Acked-by: Tigran Mkrtchyan (tigran.mkrtchyan@desy.de)
    Patch: http://rb.dcache.org/r/6253/
    Target: trunk
    Target: 2.6
    Target: 2.7
    Require-book: no
    Require-notes: no