nfsd4: eliminate impossible open replay case

If open fails with any error other than nfserr_replay_me, then the main
nfsd4_proc_compound() loop continues unconditionally to
nfsd4_encode_operation(), which will always call encode_seqid_op_tail.
Thus the condition we check for here does not occur.

Signed-off-by: J. Bruce Fields <bfields@redhat.com>