[#185] native: Issue session token on the previous epoch

Consider 2 nodes, A and B. Because of the race condition, A has epoch N,
and B has (still) epoch N-1. Creating session token and putting object
on the node A will set issuing epoch to N, thus failing validation on
the node B.

Signed-off-by: Evgenii Stratonikov <e.stratonikov@yadro.com>

internal/native/native.go

@@ -118,11 +118,16 @@ func (n *Native) Connect(endpoint, hexPrivateKey string, dialTimeout, streamTime
 	tok.SetAuthKey(&key)
 	tok.SetExp(exp)
 
+	res, err := cli.NetworkInfo(n.vu.Context(), client.PrmNetworkInfo{})
+	if err != nil {
+		return nil, err
+	}
+
+	prevEpoch := res.Info().CurrentEpoch() - 1
+	tok.SetNbf(prevEpoch)
+	tok.SetIat(prevEpoch)
+
 	if prepareLocally && maxObjSize > 0 {
-		res, err := cli.NetworkInfo(n.vu.Context(), client.PrmNetworkInfo{})
-		if err != nil {
-			return nil, err
-		}
 		if uint64(maxObjSize) > res.Info().MaxObjectSize() {
 			return nil, fmt.Errorf("max object size must be not greater than %d bytes", res.Info().MaxObjectSize())
 		}