NFSD: Remove redundant cb_seq_status initialization

As far as I can see, setting cb_seq_status in nfsd4_init_cb() is
superfluous because it is set again in nfsd4_cb_prepare().

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Benjamin Coddington <bcodding@redhat.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>