NFSv4.1: Fix regression in callback retry handling

When initializing a freshly created slot for the calllback channel,
the seq_nr needs to be 0, not 1.  Otherwise validate_seqid
and nfs4_slot_wait_on_seqid get confused and believe that the
mpty slot corresponds to a previously sent reply.
Signed-off-by: NFred Isaman <fred.isaman@gmail.com>
Signed-off-by: NTrond Myklebust <trond.myklebust@primarydata.com>

fs/nfs/nfs4session.c

@@ -169,7 +169,7 @@ bool nfs4_try_to_lock_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot)
 struct nfs4_slot *nfs4_lookup_slot(struct nfs4_slot_table *tbl, u32 slotid)
 {
 	if (slotid <= tbl->max_slotid)
-		return nfs4_find_or_create_slot(tbl, slotid, 1, GFP_NOWAIT);
+		return nfs4_find_or_create_slot(tbl, slotid, 0, GFP_NOWAIT);
 	return ERR_PTR(-E2BIG);
 }