nfsd: pass nfsd4_compound_state* to nfs4_preprocess_{state,seq}id_op

Currently we only use cstate->current_fh,
will also be used by nfsd41 code.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>