NFS v4.2 adds a CB_OFFLOAD operation used by COPY and WRITE_PLUS.  Since
neither of these operations have been implemented yet, simply return
NFS4ERR_NOTSUPP.
Signed-off-by: NBryan Schumaker <bjschuma@netapp.com>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>